IN THE UNITED STATES DISTRICT COURT FOR THE EASTERN DISTRICT OF TEXAS MARSHALL DIVISION OPTICAL TECH IP, LLC, ) ) Plaintiff, ) ) Civil Action No. __________ v. ) ) JURY TRIAL DEMANDED HUAWEI TECHNOLOGIES USA INC., ) ) Defendant. ) ) COMPLAINT For its Complaint, Plaintiff Optical Tech, LLC ("Optical Tech"), by and through the undersigned counsel, alleges as follows: THE PARTIES 1. Optical Tech is a Texas limited liability company with a place of business located at 1400 Preston Road, Suite 475, Plano, Texas 75093. 2. Defendant Huawei Technologies USA Inc. is a Texas corporation with, upon information and belief, a place of business located at 5700 Tennyson Parkway, Suite 500, Plano, Texas 75024. JURISDICTION AND VENUE 3. This action arises under the Patent Act, 35 U.S.C. § 1 et seq. 4. Subject matter jurisdiction is proper in this Court under 28 U.S.C. §§ 1331 and 1338. 5. Upon information and belief, Defendant conducts substantial business in this forum, directly or through intermediaries, including: (i) at least a portion of the infringements alleged herein; and (ii) regularly doing or soliciting business, engaging in Case 2:14-cv-01102 Document 1 Filed 12/10/14 Page 1 of 4 PageID #: 1
Transcript
IN THE UNITED STATES DISTRICT COURT FOR THE EASTERN DISTRICT OF TEXAS
MARSHALL DIVISION
OPTICAL TECH IP, LLC, )
)
Plaintiff, )
) Civil Action No. __________
v. )
) JURY TRIAL DEMANDED
HUAWEI TECHNOLOGIES USA INC., )
)
Defendant. )
)
COMPLAINT
For its Complaint, Plaintiff Optical Tech, LLC ("Optical Tech"), by and through
the undersigned counsel, alleges as follows:
THE PARTIES
1. Optical Tech is a Texas limited liability company with a place of business
located at 1400 Preston Road, Suite 475, Plano, Texas 75093.
2. Defendant Huawei Technologies USA Inc. is a Texas corporation with,
upon information and belief, a place of business located at 5700 Tennyson Parkway,
Suite 500, Plano, Texas 75024.
JURISDICTION AND VENUE
3. This action arises under the Patent Act, 35 U.S.C. § 1 et seq.
4. Subject matter jurisdiction is proper in this Court under 28 U.S.C.
§§ 1331 and 1338.
5. Upon information and belief, Defendant conducts substantial business in
this forum, directly or through intermediaries, including: (i) at least a portion of the
infringements alleged herein; and (ii) regularly doing or soliciting business, engaging in
Case 2:14-cv-01102 Document 1 Filed 12/10/14 Page 1 of 4 PageID #: 1
2
other persistent courses of conduct and/or deriving substantial revenue from goods and
services provided to individuals in this district.
6. Venue is proper in this district pursuant to §§ 1391(b), (c) and 1400(b).
THE PATENT-IN-SUIT
7. On June 29, 2010, United States Patent No. 7,747,172 (the "'172 patent"),
entitled "Optical Communication System Having Enhanced Spectral Efficiency Using
Electronic Signal Processing" was duly and lawfully issued by the U.S. Patent and
Trademark Office. A true and correct copy of the '172 patent is attached hereto as
Exhibit A.
8. Optical Tech is the assignee and owner of the right, title and interest in
and to the '172 patent, including the right to assert all causes of action arising under said
patents and the right to any remedies for infringement of them.
COUNT I – INFRINGEMENT OF U.S. PATENT NO. 7,747,172
9. Optical Tech repeats and realleges the allegations of paragraphs 1 through
8 as if fully set forth herein.
10. Without license or authorization and in violation of 35 U.S.C. § 271(a),
Defendant has infringed and continues to infringe the '172 patent by making, using,
importing, offering for sale, and/or selling optical communication systems, including, but
not limited to OptiX ONS 8800 Intelligent Optical Transport Platforms, covered by one
or more claims of the '172 patent.
11. More specifically and upon information and belief, the OptiX ONS 8800
Intelligent Optical Transport Platform includes tunable filters used to filter data channels
prior to each optical transmitter. Multiple channels of differing bandwidth coexist in the
same spectrum thus bandwidth-limiting is performed to provide a functional optical
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transmission. See OptiX OSN 8800 T64/T32 Intelligent Optical Transport Platform
V100R006C00 Product Overview, Issue 3 (2011-09-15) at 37; IBM Redpaper, IBM
System z Qualified DWDM: Huawei Optix OSN 8800 Release 5.51.07.36 and Optix
OSN 1800 Release 5.67.03.22 at 11. The OptiX ONS 8800 Intelligent Optical Transport
Platform outputs the pre-filtered data channels from an optical transmitter to create a
functional transmission. See IBM Redpaper, IBM System z Qualified DWDM: Huawei
Optix OSN 8800 Release 5.51.07.36 and Optix OSN 1800 Release 5.67.03.22 at 11;
OptiX OSN 8800 T64/T32 Intelligent Optical Transport Platform V100R006C00 Product
Overview, Issue 3 (2011-09-15) at 1, 49. The OptiX ONS 8800 Intelligent Optical
Transport Platform contains an optical receiver that performs digital equalization. See
OptiX OSN 8800 T64/T32 Intelligent Optical Transport Platform V100R006C00 Product
Overview, Issue 3 (2011-09-15) at 43. Equalization is performed to compensate for the
pre-filtering applied to the channels of the data transmitter, and each channel can be pre-
filtered at the transmitter as well. See OptiX OSN 8800 T64/T32 Intelligent Optical
Transport Platform V100R006C00 Product Overview, Issue 3 (2011-09-15) at 23.
12. Optical Tech is entitled to recover from Defendant the damages sustained
by Optical Tech as a result of Defendant's infringement of the '172 patent in an amount
subject to proof at trial, which, by law, cannot be less than a reasonable royalty, together
with interest and costs as fixed by this Court under 35 U.S.C. § 284.
PRAYER FOR RELIEF
WHEREFORE, Optical Tech requests that this Court enter judgment against
Defendant as follows:
A. An adjudication that Defendant has infringed the '172 patent;
Case 2:14-cv-01102 Document 1 Filed 12/10/14 Page 3 of 4 PageID #: 3
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B. An award of damages to be paid by Defendant adequate to compensate
Optical Tech for Defendant's past infringement of the '172 patent and any continuing or
future infringement through the date such judgment is entered, including interest, costs,
expenses and an accounting of all infringing acts including, but not limited to, those acts
not presented at trial;
C. A declaration that this case is exceptional under 35 U.S.C. § 285, and an
award of Optical Tech's reasonable attorneys' fees; and
D. An award to Optical Tech of such further relief at law or in equity as the
398/27; 398/159; 398/193 Field of Classi?cation Search ................. .. 398/25,
398/26, 147, 149, 158, 159, 1924194, 199, 398/ 27
See application ?le for complete search history.
(56) References Cited
U.S. PATENT DOCUMENTS
6,961,373 B2 * 11/2005 Jones ....................... .. 375/232
7,471,904 B2 * 12/2008 Kaneda et al. ............ .. 398/208
2005/0058461 A1* 3/2005 Lee et al. .................. .. 398/198
2006/0034618 A1* 2/2006 Chen et al. ................ .. 398/198
2007/0222654 A1* 9/2007 VraZel et al. .............. .. 341/144
OTHER PUBLICATIONS
Hayee, M. 1., et al., “Enhancing spectral ef?ciency of binary NRZ optical networks with electronic signal processing,” vol. 5, No. 9, Sep. 2006, Journal of Optical Network, pp. 655-661. Haddad, R., et al., “Spectral Ef?ciency of up to 1.6 bit/sec/HZ in Binary NRZ WDM Systems using Electronic Signal Processing,” Optical Society ofAmerica, 2005, pp. 1-2.
* cited by examiner
Primary ExamineriDalZid Singh (74) Attorney, Agent, or FirmiPotomac Patent Group PLLC
(57) ABSTRACT
An optical communication system combines strong electrical pre-?ltering of data at the transmitter and digital feedback equalization (DFE) at the receiver to enhance spectral e?i ciency. The system can be applied to optical networking and digital communication systems, including binary modulated systems optical network systems.
30 Claims, 4 Drawing Sheets
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Case 2:14-cv-01102 Document 1-1 Filed 12/10/14 Page 6 of 10 PageID #: 10
US 7,747,172 B2 1
OPTICAL COMMUNICATION SYSTEM HAVING ENHANCED SPECTRAL
EFFICIENCY USING ELECTRONIC SIGNAL PROCESSING
RELATED APPLICATIONS
This application claims priority to US. Patent Application No. 60/799,244, ?led May 10, 2006, the disclosure ofwhich is hereby incorporated by reference.
TECHNICAL FIELD
The invention relates to ?ber optic communications and optical communication systems, such as metropolitan optical networks or the like.
BACKGROUND
Fiber optic communication generally involves modulating optical signals at high bit rates and transmitting the modu lated optical signals over optical ?bers. For example, in a wavelength division multiplexed (WDM) ?ber optic commu nications system, optical carrier signals at a sequence of distinct wavelengths are separately modulated by informa tion channels and then multiplexed onto a single optical ?ber. Efforts continue toward increasing the data capacity of ?ber optic communications systems. One of the key features of a wavelength division multi
plexed (WDM) system is spectral e?iciency, which deter mines how many bits/ sec of data canbe transmittedper unit of available bandwidth. The available bandwidth in practical WDM systems is limited by optical ampli?ers which are used to periodically boost the optical power for a given transmis sion length. However, upgrading the capacity of existing opti cal networks by replacing in-ground ?ber and ampli?ers is extremely costly. Various techniques have been proposed to enhance the spectral ef?ciency of WDM systems to improve spectral ef?ciency (i.e., bits per second transmitted per unit of available bandwidth) of the existing optical infrastructure. That is, because of the cost associated with upgrading or replacing the available WDM bandwidth, various techniques have been proposed to enhance the spectral ef?ciency of WDM systems to approach or exceed 1 bit/sec/HZ, which is the theoretical limit for a simple binary modulation format.
However, most of these techniques involve either complex binary modulation formats to limit the channel bandwidth for a given data rate, or an attempt to take advantage of multi level modulation formats and polarization division multiplex ing to increase the spectral ef?ciency. However, many of these complex techniques require costly transmitters and receivers with specialiZed, expensive electronics.
SUMMARY
In general, techniques are described herein for combining strong electrical pre-?ltering of data at a transmitter with digital feedback equaliZation (DFE) at a receiver to enhance the spectral ef?ciency of ?ber optic communication. The techniques can be applied to optical networking and digital communication systems, including binary NRZ intensity modulated systems optical network systems.
In certain embodiments, pre-?ltering of each data channel at the transmitter is accomplished using an electrical low pass ?lter (LPF) before optical intensity modulation in order to limit the channel bandwidth. That is, in order to limit the frequency spreading of the data channels, each data channel is
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2 pre-?ltered prior to any modulation and multiplexing of the data channels into the ?ber link. This pre-?ltering effectively “clips” the frequency spreading of each of the data channels in the frequency domain, and allows for reduced channel spacing at the transmitter. As a result, the data channels can be “packed” closer within the frequency spectrum, thereby enhancing spectral ef?ciency of the optical transmission.
However, the incorporation of the pre-?ltering at the trans mitter induces severe inter-symbol interference (ISI) in each WDM channel. Therefore, DFE is employed at the receiver to electronically compensate for the ISI that was induced by strong pre-?ltering of individual channels at the transmitter. In other words, DFE within the receiver is used to compensate for signal distortion that was intentionally introduced at the transmitter prior to optical transmission in order to reduce channel spacing, as opposed to compensation for ISI or other effects introduced by transmission through the optical chan nel. In this manner, pre-?ltering at the transmitter and equal iZation at the receiver may be utiliZed in combination so as to enhance the spectral ef?ciency of a WDM system. The details of one or more embodiments of the invention
are set forth in the accompanying drawings and the descrip tion below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic diagram of the WDM system employ ing pre-?lter at transmitter and decision feedback equaliZer at receiver. LD is a laser diode, PD is a photo-detector, DC is a decision circuit and T is a bit time delay. Please note that Al to An are at orthogonal polarizations.
FIG. 2 is a graph showing the eye opening vs. number of feed forward tap ?lters for different numbers of feedback tap ?lters. Spectral ef?ciency is 1 bit/sec/HZ.
FIG. 3 is a graph showing eye opening vs. spectral e?i ciency with and without proposed scheme for a back to back 10.7 Gb/ s WDM system. The eyes in the right hand side are (i) with pre-?ltering+DFE, (ii) with pre-?ltering but no DFE, and (iii) without pre-?ltering and no DFE.
FIG. 4 is a block diagram showing a simulated ?ber link employing a typical terrestrial dispersion map using standard single mode ?ber and Erbium doped ?ber ampli?ers.
FIG. 5 is a graph showing eye opening vs. average channel power for spectral ef?ciencies of 1.6 bit/sec/HZ (circles) and 1.0 bit/sec/HZ (squares). Solid circles and squares represent the proposed scheme and hollow circles and squares represent the ordinary WDM system.
FIG. 6 is a graph showing Q Factor vs. average channel power for spectral ef?ciencies of 1.6 bit/sec/HZ with 400 km transmission distance and 1.0 bit/sec/HZ with 800 km trans mission distance.
FIG. 7 is a graph showing a comparison of system Q for bit synchronous and fractionally spaced (FF tapped delay:T/3) DFE for 400 km system with spectral ef?ciency of 1.6 bit/ sec/HZ and 800 km system with spectral ef?ciency of 1.0 bit/sec/HZ.
DETAILED DESCRIPTION
FIG. 1 is a block diagram of an example communication system 2 employing the electronic signal processing tech niques to enhance spectral ef?ciency. At the transmitter 4, a ?lter 3, e.g., an electrical low pass ?lter (LPF), is used to pre-?lter each data channel (data) by limiting the bandwidth of each data channel prior to modulation. In one embodiment,
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US 7,747,172 B2 3
a Bessel shaped LPF of order 10 is used for pre-?ltering. The 3-dB bandwidth of the pre-?lter may be selected to reduce or minimize the crosstalk for a given channel spacing. The desired 3-dB bandwidth of the pre-?lter may be 3.5 GHZ for a spectral ef?ciency of 1 bit/sec/HZ (channel spacing:10 GHZ). After pre-?ltering, each data channel is optically modulated by a modulator (Mod), such as a Mach-Zehnder Interferometer (MZI) based modulator or other form of modulator suitable for optical communication. All the modu lated channels are then multiplexed (MUX) together for transmission into the ?ber link 5. As one example, in one embodiment, 11 channels may be
multiplexed With orthogonal polariZations of alternate Wave lengths at the data rate of 10.7 Gb/ s each to have an effective spectral ef?ciency of 1 bit/sec/HZ. A 10.7 Gb/s data rate can be used to include 7% forWard error correction (FEC) over head. To evaluate the effectiveness of the technique in back to-back con?guration, receiver 6 includes a bandpass ?lter (BPF) to demultiplex the middle of 11 simulated channels (FIG. 1). As one example, a 2'” order Gaussian shaped band pass ?lter (BPF) may be used With 3-dB bandWidth of 11 GHZ, Which can be tuned to limit the crosstalk for 10 GHZ channel spacing With orthogonally launched adjacent chan nels.
After BPF, the optical signal is photo-detected (PD) and passed through an electrical LPF, e.g., an LPF With 3-dB bandWidth of 7.5 GHZ. FIG. 1 shoWs one example in Which, after LPF, an eye diagram 7 of the middle channel, Where the eye diagram is a graph that superimposes data bits received versus time. Severe ISI induced by pre-?ltering can be seen in eye diagram 7, Which is due to distortion (i.e., ISI) introduced by the intentional pre-?ltering of each data channel by ?lter 3. In the example of FIG. 1, Receiver 6 includes a decision feedback equalizer (DFE) 10 comprising n feed forWard (FF) and m feedback (FB) tapped delay ?lters 12 to compensate for the ISI introduced by ?lter 3. Bit synchronous tapped delay ?lters i.e., the delay is one bit time (T), may be used. Other equalizers could be used, e.g., Maximum Sequence Likeli hood Estimation (MSLE) orV1terbi Decoding, to compensate for the ISI resulting from the intentional pre-?ltering at the transmitter 4.
In one embodiment, the coef?cients (dl . . . dm, cO . . . c”)
may be adaptive. For example, the coef?cients (dl . . . dm, cO . . . c”) of FF and EB tapped delay ?lters may be adapted by sending a long sequence of randomly generatedbits andusing the least mean square (LMS) algorithm until the coef?cients become stationary. The Weights of the coef?cients can be
d1, d2, . . . dm]. The
LMS algorithm updates 6) With each incoming bit:
a
represented by avector C :[co, cl, . . . c in!
(1),
Q
Where C (1“) represents the tap vector Weights at time kT, A is the scale factor that controls the rate of adaptation and ek is the error signal betWeen the decision sample and the decision
output. The vector €:[vk, vk_l, . . . , ck_(n_n), Ik_l), dk_2, . . . , dk_m], Where vk_l- is the input signal at time (k—i)T and I 1H. is the decision made at time (k—i)T.
Alternatively, since DFE 10 is being used to compensate for a knoWn, intentional level of signal distortion resulting from ?lter 3 of transmitter 4, the coef?cients (dl . . . dm,
cO . . . c”) may be pre-computed, thereby conversing compu tation resources and reducing complexity of receiver 6. That is, coef?cients (dl . . . dm, cO . . . c”) need not be adaptive based
on an error signal, but rather set as a function of the amount of
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4 distortion that Was intentionally introduced at the transmitter in order to tightly pack the data channels Within the optical transmission. These stationary coef?cients in DFE 10 of receiver 6 (as shoWn in FIG. 1) can be used to equaliZe the ISI induced by the pre-?ltering of the channels at transmitter 4.
In the example of FIG. 1, a different sequence of 213 pseudorandom bits can be used to obtain an eye diagram 9 just before the sampler for the decision circuit (part of the DFE). Eye diagram 9 of the middle channel is also shoWn in FIG. 1 (left of the tWo) using 8 FE and 2 FB tapped delay ?lters. More than 90% eye opening, as shoWn in eye diagram 9, shoWs that ISI induced by pre-?ltering can be very e?iciently compen sated, proving the effectiveness of the technique of combin ing pre-?ltering at transmitter and DFE at the receiver to enhance the spectral ef?ciency binary intensity modulated systems.
In the example of FIG. 1, the eye diagram 9 of FIG. 1 can be produced using 8 FE and 2 FB tapped delay ?lters. FIG. 2 illustrates example criteria for choosing a desirable number of FF and EB tapped delay ?lters for DFE 10 in Which eye opening of 10 GHZ spaced system is shoWn versus number of FF tapped delay ?lters for 0, 2 and 4 FB tapped delay ?lters. One can see from FIG. 2 that effectiveness of DFE improves With increasing the number of FF tapped delay ?lters up to 8 beyond Which the improvement in performance saturates.
Similarly, FIG. 2 also shoWs that increasing the FB tapped delay ?lters beyond 2 does not bring any further improvement for a 10 GHZ spaced system. The optimum number of tapped delay ?lters may depend upon the amount of ISI to be com pensated, and therefore may depend upon the channel spacing (spectral ef?ciency) for Which pre-?ltering bandWidth is opti miZed. That is, the number of n feed forward (FF) and m feedback (FB) tapped delay ?lters 12 can be selected as a function of an amount of ?ltering applied by the ?lter 3 of the transmitter 4, Which directly relates to the channel spacing that may be used by transmitter 4. Similarly, one can perform the same analysis With a 6.25 GHZ spaced system and deter mine that acceptable performance can be achieved by using 8 FE and 4 FB tapped delay ?lters. For the 6.25 GHZ spaced ?lter, for example, an optimiZed pre-?lter bandWidth may be approximately 2.5 GHZ. The back-to-back system performance can be analyZed by
varying the spectral ef?ciency both With and Without pre ?ltering and DFE. Exemplary results of such an analysis are shoWn in FIG. 3 in Which eye opening is plotted vs. spectral ef?ciency With and Without pre-?ltering and DFE. At loWer spectral ef?ciency of 0.4 bit/sec/HZ (channel spacing:25 GHZ), performance With the use of pre-?ltering and DFE is only slightly better than a regular NRZ WDM system because the crosstalk is small at such a large channel spacing. HoW ever When the spectral ef?ciency is increased, the crosstalk increases due to reduced channel spacing and hence severely degrades the performance of regular NRZ WDM system. At high spectral ef?ciency the technique using pre-?ltering and DFE improves the system performance signi?cantly by almost completely eliminating the crosstalk using pre-?lter ing and e?iciently compensating the resulting ISI using DFE. At the spectral e?iciency of 1.6 bit/sec/HZ, the eye may be completely closed Without using pre-?ltering and DFE shoW ing the system may not Work With regular NRZ WDM scheme, Whereas the pre-?ltering and DFE may open the completely closed eye by more than 50%. Notably, a pre ?ltered eye diagram Without DFE at the spectral ef?ciency of 1.6 bit/sec/HZ is also shoWn in FIG. 3. The pre-?ltered eye is also fully closed but not due to crosstalk but rather due to severe ISI induced by a narroW pre-?ltering With the band Width of 2.5 GHZ Which is optimiZed for 6.25 GHZ channel
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spacing. This ISI can be partially compensated using DFE and thereby opening the eye by more than 50%.
After back-to-back analysis, We analyzed the performance of the pre-?ltering and DFE scheme by transmitting through a typical terrestrial dispersion map based upon SSMF shoWn in FIG. 4. The dispersion map consisted of 100 km spans of SSMF folloWed by a tWo stage EDFA having 20 km of dis persion compensating ?ber (DCF) in betWeen the tWo stages to compensate the dispersion of each span. The path average dispersion Was assumed to be non-Zero (-0.5 ps/nm-km per span) and Was compensated using a ?xed post-dispersion compensation at the receiver. The total span loss including the DCF is 35 dB and the noise ?gure of each EDFA Was 6 dB. The dispersion values of SME and DCF Were 17 and —85 ps/nm-km, respectively. The effective areas of SME and DCF Were assumed to be 75 and 20 um2. An independent pseudorandom bit stream of 213 bits Was
transmitted on each of 11 channels through this dispersion map using pre-?ltering at the transmitter and DFE at the receiver. Propagation of a Wavelength multiplexed signal Was simulated by solving nonlinear Schrodinger equation using split step Fourier scheme. The simulated nonlinear effects are self-phase modulation (SPM), cross-phase modulation (XPM) and four-Wave mixing (FWM). In the ?rst step We ignored the ampli?ed stimulated emission (ASE) noise and carried out noiseless simulation to estimate the performance of pre-?ltering and DFE in presence of ?ber nonlinearity.
The resulting eye opening of the middle channel vs. aver age poWer/channel is shoWn in FIG. 5 for the transmission distance of 400 km With spectral e?iciency of 1.6 bit/sec/HZ and for the transmission distance of 800 km With the spectral ef?ciency of 1 bit/sec/HZ. A total of 11 channels Were simu lated to ensure that XPM due to neighboring channels Was properly included (5 signi?cant neighboring channels on each side). We varied the number of simulated channels from 3 to 19 and found that the WDM nonlinear penalty due to XPM and FWM did not signi?cantly increase When WDM channels are increased beyond 11. For comparison purpose, the eye opening as a result of no pre-?ltering and no DFE is also shoWn in FIG. 5 for the corresponding distances and spectral e?iciencies. We can see that the eye opening decreases With increasing channel poWer due to ?ber nonlin earities but still performs signi?cantly better than the case Without pre-?ltering and DFE. The spectral ef?ciency of 1.6 bit/sec/HZ, the eye Was totally closed Without using pre-?l tering and DFE due to severe inter-channel crosstalk. Simi larly, at the spectral ef?ciency of 1 bit/sec/HZ, the eye Was less than 30% open Without using the pre-?ltering and DFE and Was mainly degraded by crosstalk rather than nonlinearity. Therefore, eye opening decreases sloWly With increasing channel poWer.
To estimate the bit error rate (BER) performance, We ana lyZed the above system by adding the accumulated noise at the receiver just before the photo-detection. We repeated the full receiver processing including DFE one hundred times by adding different optical noise each time. We then obtained the average and standard deviation of each bit just before the decision circuit in DFE. By assuming the Gaussian noise distribution, a BER Was then calculated for each bit and then an average BER Was obtained. The average BER Was then converted to a Q factor. The resulting Q factors for the WDM systems With spectral ef?ciencies of 1.6 bit/sec/HZ (400 km system) and 1.0 bit/sec/HZ (800 km system) are shoWn in FIG. 6 vs. average channel poWer. The Q factor increases With increasing channel poWer due to better signal-to-noise ratio (SNR) and beyond a certain channel poWer, ?ber nonlinearity increases too much and degrades the system performance.
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6 The optimal Q’s of 14.1 and 16 dB are obtained respectively for the transmission distance of 400 km With 1.6 bit/sec/HZ spectral ef?ciency and 800 km With 1.0 bit/sec/HZ of spectral e?iciency. We used an FEC overhead of 7% Which Will give an additional gain in Q of at least 5 dB. This suggests the feasibility of a 1.6 bit/sec/HZ of spectral ef?ciency for met ropolitan distances using the pre-?ltering and DFE technique.
Next, the performance of fractionally spaced DFE in improving spectral ef?ciency Was compared to bit synchro nous DFE. In bit synchronous DFE, both FF and EB tapped delay ?lters use a delay of one bit time (T). On the contrary, fractionally spaced DFE, FF tapped delays are only a fraction of one bit time While FB tapped delays are still one bit time. A delay of T/3 for FF tapped delay ?lters Was used for frac tionally spaced DFE. With fractionally spaced DFE, the num ber of FF tapped delay ?lters are increased by three times to include the same number of bits as in bit synchronous DFE. The performance of 400 km system With the spectral e?i ciency of 1.6 bit/sec/HZ Was compared With 800 km system With the spectral ef?ciency of 1 bit/sec/HZ using bit synchro nous and fractionally spaced DFE. The optimum perfor mance of these tWo systems Was 14.1 and 16 dB of Q at the optimum poWer levels of —3 and —2 dBm/channel, respec tively for bit synchronous DFE case (FIG. 6).
These systems Were again simulated at these poWer levels With fractionally spaced DFE (FF tapped delay:T/3). The corresponding results are shoWn in FIG. 7 Where the optimal Q values of bit synchronous and fractionally spaced DFE are plotted side by side. The Q improvement is 0.6 dB in 400 km system With spectral ef?ciency of 1.6 bit/sec/HZ, While a Q improvement of only 0.3 dB is obtained in 800 km system With spectral ef?ciency of 1 bit/sec/HZ. The improvement is slightly better in the case of spectral ef?ciency of 1.6 bit/sec/ HZ because of more ISI due to stronger pre-?ltering Which is better compensated by fractionally spaced DFE.
Various embodiments of the invention have been described for utiliZing electronic signal processing Within an optical receiver to compensate ISI induced by strong pre-?ltering of data at the optical transmitter to enhance the spectral e?i ciency of an optical communication system, such as a binary NRZ WDM system. In one embodiment, a 10.7 Gb/s WDM system employing pre-?ltering at the transmitter and elec tronic signal processing at the receiver Was analyZed using orthogonal polarization launch for alternate channel Wave lengths. A transmission distance of up to 400 km Was achiev able With this exemplary embodiment With spectral ef?ciency of up to 1.6 bit/sec/HZ (channel spacing 6.25 GHZ) on typical terrestrial dispersion maps employing standard single mode ?ber (SSMF) and erbium doped ?ber ampli?ers (EDFAs). Channel spacing of 6.25 GHZ for 10.7 Gb/s data rate is oth erWise impossible in binary NRZ systems because of severe cross-talk. The described techniques can be embodied in a variety of
optical transmitters, receivers, and/ or transceivers for optical communication systems or netWorks. The devices may include a general-purpose processor, embedded processor, digital signal processor (DSP), ?eld programmable gate array (FPGA), application speci?c integrated circuit (ASIC) or similar hardWare, ?rmWare and/or software for implementing the techniques described herein. If implemented in softWare, a computer-readable storage medium may store computer readable instructions, i.e., program code, that can be executed by a processor or DSP to carry out one of more of the tech niques described above. For example, the computer-readable storage medium may comprise random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NV RAM), electrically erasable program
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mable read-only memory (EEPROM), ?ash memory, or the like. These and other embodiments are Within the scope of the following claims.
The invention claimed is: 1. An optical communication system comprising: a transmitter having a ?lter that pre-?lters each of a plural
ity of data channels to limit the bandwidth of each of said plurality of data channels and outputs an optical trans mission Which includes the pre-?ltered data channels; and
a receiver having an equalizer that applies digital equaliZa tion to the optical transmission, said digital equalization con?gured to compensate for the pre-?ltering of the data channels at the transmitter.
2. The optical communication system of claim 1, Wherein said ?lter cuts off high frequency components associated With said plurality of data channels to generate said pre-?ltered data channels having a format that achieves a spectral e?i ciency that equals or exceeds 1 bit/sec/HZ.
3. The optical communication system of claim 1, Wherein said transmitter further comprises a modulator and Wherein the modulator applies a binary modulation format to each of the pre-?ltered data channels.
4. The optical communication system of claim 3, Wherein the modulator comprises a non-retum to Zero (NRZ) intensity modulator.
5. The optical communication system of claim 1, Wherein the ?lter of the transmitter limits the frequency spreading of each of the data channels in the frequency domain and alloWs for reduced channel spacing Within the optical transmission.
6. The optical communication system of claim 1, Wherein the ?lter of the transmitter comprises an electrical loW pass ?lter (LPF).
7. The optical communication system of claim 6, Wherein the loW pass ?lter comprises a Bessel shaped LPF of order 10.
8. The optical communication system of claim 1, Wherein the digital equaliZer comprises a digital feedback equaliZer (DFE).
9. The optical communication system of claim 8, Wherein the DFE electronically compensates for inter-symbol inter ference (1S1) induced by the pre-?lter at the transmitter.
10. The optical communication system of claim 8, Wherein the DFE of the receiver contains n feed forWard (FF) and m feedback (FB) tapped delay ?lters.
11. The optical communication system of claim 10, Wherein n and m are a function of an amount of ?ltering applied by the ?lter of the transmitter.
12. The optical communication system of claim 10, Wherein n and m are a function of a channel spacing used by the transmitter for the data channels When outputting the optical transmission.
13. The optical communication system of claim 10, Wherein the DFE of the receiver contains no more than 8 PF and no more than 2 FB tapped delay ?lters.
14. The optical communication system of claim 1, Wherein the equaliZer of the receiver compensates for distortion in the signal that Was intentionally introduced at the transmitter.
15. The optical communication system of claim 1, Wherein coef?cients of the equaliZer are determined as a function of an amount of distortion intentionally introduced Within the data channels by the ?lter of the transmitter.
16. The optical communication system of claim 1, Wherein coef?cients of the equaliZer are adaptively computed to mini miZe error Within the optical transmission.
17. The optical communication system of claim 1, Wherein the equaliZer of the receiver outputs a stream of detected bits from the equaliZed optical transmission.
5
5
20
25
30
35
40
45
50
55
60
65
8 18. The optical communication system of claim 1, Wherein
the equaliZer comprises a Maximum Sequence Likelihood Estimation (MSLE) equaliZer or a Viterbi Decoder.
19. A method comprising: pre-?ltering, at an optical transmitter, each of a plurality of
data channels to limit a bandWidth for each of the data
channels; outputting the pre-?ltered data channels from the optical
transmitter in the form of an optical transmission; and applying digital equaliZation to the optical transmission at
an optical receiver to compensate for the pre-?ltering of the data channels at the transmitter.
20. The method of claim 19, Wherein pre-?ltering com prises ?ltering the plurality of data channels into a format that achieves a spectral ef?ciency that equals or exceeds 1 bit/sec/ HZ.
21. The method of claim 20, further comprises modulating the pre-?ltered data channels by applying a binary modula tion format to each of the pre-?ltered data channels.
22. The method of claim 19, Wherein pre-?ltering com prises applying a loW pass ?lter to limit frequency spreading of each of the data channels so as to alloW for reduced channel spacing Within the optical transmission.
23. The method of claim 19, Wherein applying digital equaliZation comprises applying digital feedback equaliZa tion (DFE) at the receiver to electronically compensate for inter-symbol interference (1S1) induced by the pre-?ltering of the data channels at the transmitter.
24. The method of claim 23, further comprising selecting a number n of feed forWard (FF) and a number m of feedback (FB) tapped delay ?lters of a digital feedback equaliZer of the receiver as a function of an amount of the pre-?ltering to the data channels at the transmitter.
25. The method of claim 23, further comprising selecting a number n of feed forWard (FF) and a number m of feedback (FB) tapped delay ?lters of a digital feedback equaliZer of the receiver as a function of a channel spacing used by the trans mitter for the data channels When outputting the optical trans mission.
26. The method of claim 23, further comprising selecting coef?cients of a digital feedback equaliZer of the receiver as a function of an amount of distortion intentionally introduced Within the data channels by the ?ltering of the transmitter.
27. A computer-readable medium comprising instructions for causing a programmable processor to perform a method of claim 19.
28. An optical transmitter that pre-?lters each of a plurality of data channels prior to modulation of the data channels to limit a bandWidth of each of said plurality of data channels and output of an optical transmission, Wherein application of digital feedback equaliZation to the optical transmission com pensates for the pre-?ltering of the data channels and alloWs bit detection.
29. The method of claim 19, Wherein applying digital equaliZation comprises applying Maximum Sequence Like lihood Estimation (MSLE) or a Viterbi Decoding.
30. An optical receiver comprising: a photo detector to receive an optical transmission Where
each of a plurality of data channels prior of the transmis sion have been pre-?ltered to limit a bandWidth of the data channels; and
a digital feedback equaliZer (DFE) that applies digital feed back equaliZation to the optical transmission to compen sate for the pre-?ltering of the data channels at the trans mitter.
Case 2:14-cv-01102 Document 1-1 Filed 12/10/14 Page 10 of 10 PageID #: 14
OJS 44 (Rev. 12/07) CIVIL COVER SHEETThe JS 44 civil cover sheet and the information contained herein neither replace nor supplement the filing and service of pleadings or other papers as required by law, except as providedby local rules of court. This form, approved by the Judicial Conference of the United States in September 1974, is required for the use of the Clerk of Court for the purpose of initiatingthe civil docket sheet. (SEE INSTRUCTIONS ON THE REVERSE OF THE FORM.)
I. (a) PLAINTIFFS DEFENDANTS
(b) County of Residence of First Listed Plaintiff County of Residence of First Listed Defendant(EXCEPT IN U.S. PLAINTIFF CASES) (IN U.S. PLAINTIFF CASES ONLY)
NOTE: IN LAND CONDEMNATION CASES, USE THE LOCATION OF THE LAND INVOLVED.
II. BASIS OF JURISDICTION (Place an “X” in One Box Only) III. CITIZENSHIP OF PRINCIPAL PARTIES(Place an “X” in One Box for Plaintiff(For Diversity Cases Only) and One Box for Defendant)
’ 1 U.S. Government ’ 3 Federal Question PTF DEF PTF DEFPlaintiff (U.S. Government Not a Party) Citizen of This State ’ 1 ’ 1 Incorporated or Principal Place ’ 4 ’ 4
of Business In This State
’ 2 U.S. Government ’ 4 Diversity Citizen of Another State ’ 2 ’ 2 Incorporated and Principal Place ’ 5 ’ 5Defendant (Indicate Citizenship of Parties in Item III) of Business In Another State
Citizen or Subject of a ’ 3 ’ 3 Foreign Nation ’ 6 ’ 6 Foreign Country
IV. NATURE OF SUIT (Place an “X” in One Box Only)CONTRACT TORTS FORFEITURE/PENALTY BANKRUPTCY OTHER STATUTES
’ 110 Insurance PERSONAL INJURY PERSONAL INJURY ’ 610 Agriculture ’ 422 Appeal 28 USC 158 ’ 400 State Reapportionment’ 120 Marine ’ 310 Airplane ’ 362 Personal Injury - ’ 620 Other Food & Drug ’ 423 Withdrawal ’ 410 Antitrust’ 130 Miller Act ’ 315 Airplane Product Med. Malpractice ’ 625 Drug Related Seizure 28 USC 157 ’ 430 Banks and Banking’ 140 Negotiable Instrument Liability ’ 365 Personal Injury - of Property 21 USC 881 ’ 450 Commerce’ 150 Recovery of Overpayment ’ 320 Assault, Libel & Product Liability ’ 630 Liquor Laws PROPERTY RIGHTS ’ 460 Deportation
Student Loans ’ 340 Marine PERSONAL PROPERTY Safety/Health ’ 490 Cable/Sat TV (Excl. Veterans) ’ 345 Marine Product ’ 370 Other Fraud ’ 690 Other ’ 810 Selective Service
’ 153 Recovery of Overpayment Liability ’ 371 Truth in Lending LABOR SOCIAL SECURITY ’ 850 Securities/Commodities/ of Veteran’s Benefits ’ 350 Motor Vehicle ’ 380 Other Personal ’ 710 Fair Labor Standards ’ 861 HIA (1395ff) Exchange
’ 160 Stockholders’ Suits ’ 355 Motor Vehicle Property Damage Act ’ 862 Black Lung (923) ’ 875 Customer Challenge’ 190 Other Contract Product Liability ’ 385 Property Damage ’ 720 Labor/Mgmt. Relations ’ 863 DIWC/DIWW (405(g)) 12 USC 3410’ 195 Contract Product Liability ’ 360 Other Personal Product Liability ’ 730 Labor/Mgmt.Reporting ’ 864 SSID Title XVI ’ 890 Other Statutory Actions’ 196 Franchise Injury & Disclosure Act ’ 865 RSI (405(g)) ’ 891 Agricultural Acts
REAL PROPERTY CIVIL RIGHTS PRISONER PETITIONS ’ 740 Railway Labor Act FEDERAL TAX SUITS ’ 892 Economic Stabilization Act’ 210 Land Condemnation ’ 441 Voting ’ 510 Motions to Vacate ’ 790 Other Labor Litigation ’ 870 Taxes (U.S. Plaintiff ’ 893 Environmental Matters’ 220 Foreclosure ’ 442 Employment Sentence ’ 791 Empl. Ret. Inc. or Defendant) ’ 894 Energy Allocation Act’ 230 Rent Lease & Ejectment ’ 443 Housing/ Habeas Corpus: Security Act ’ 871 IRS—Third Party ’ 895 Freedom of Information’ 240 Torts to Land Accommodations ’ 530 General 26 USC 7609 Act’ 245 Tort Product Liability ’ 444 Welfare ’ 535 Death Penalty IMMIGRATION ’ 900Appeal of Fee Determination’ 290 All Other Real Property ’ 445 Amer. w/Disabilities - ’ 540 Mandamus & Other ’ 462 Naturalization Application Under Equal Access
Employment ’ 550 Civil Rights ’ 463 Habeas Corpus - to Justice’ 446 Amer. w/Disabilities - ’ 555 Prison Condition Alien Detainee ’ 950 Constitutionality of
Other ’ 465 Other Immigration State Statutes’ 440 Other Civil Rights Actions
V. ORIGINTransferred fromanother district(specify)
Appeal to DistrictJudge fromMagistrateJudgment
(Place an “X” in One Box Only)’ 1 Original
Proceeding’ 2 Removed from
State Court’ 3 Remanded from
Appellate Court’ 4 Reinstated or
Reopened’ 5 ’ 6 Multidistrict
Litigation’ 7
VI. CAUSE OF ACTIONCite the U.S. Civil Statute under which you are filing (Do not cite jurisdictional statutes unless diversity): Brief description of cause:
VII. REQUESTED IN COMPLAINT:
’ CHECK IF THIS IS A CLASS ACTIONUNDER F.R.C.P. 23
DEMAND $ CHECK YES only if demanded in complaint:JURY DEMAND: ’ Yes ’ No
VIII. RELATED CASE(S) IF ANY (See instructions): JUDGE DOCKET NUMBER
DATE SIGNATURE OF ATTORNEY OF RECORD
FOR OFFICE USE ONLY
RECEIPT # AMOUNT APPLYING IFP JUDGE MAG. JUDGE
Case 2:14-cv-01102 Document 1-2 Filed 12/10/14 Page 1 of 2 PageID #: 15
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2:14-cv-1026, 1027, 1029
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JS 44 Reverse (Rev. 12/07)
INSTRUCTIONS FOR ATTORNEYS COMPLETING CIVIL COVER SHEET FORM JS 44
Authority For Civil Cover Sheet
The JS 44 civil cover sheet and the information contained herein neither replaces nor supplements the filings and service of pleading or other papers as requiredby law, except as provided by local rules of court. This form, approved by the Judicial Conference of the United States in September 1974, is required for the useof the Clerk of Court for the purpose of initiating the civil docket sheet. Consequently, a civil cover sheet is submitted to the Clerk of Court for each civil complaintfiled. The attorney filing a case should complete the form as follows:
I. (a) Plaintiffs-Defendants. Enter names (last, first, middle initial) of plaintiff and defendant. If the plaintiff or defendant is a government agency, use onlythe full name or standard abbreviations. If the plaintiff or defendant is an official within a government agency, identify first the agency and then the official, givingboth name and title.
(b) County of Residence. For each civil case filed, except U.S. plaintiff cases, enter the name of the county where the first listed plaintiff resides at the timeof filing. In U.S. plaintiff cases, enter the name of the county in which the first listed defendant resides at the time of filing. (NOTE: In land condemnation cases,the county of residence of the “defendant” is the location of the tract of land involved.)
(c) Attorneys. Enter the firm name, address, telephone number, and attorney of record. If there are several attorneys, list them on an attachment, notingin this section “(see attachment)”.
II. Jurisdiction. The basis of jurisdiction is set forth under Rule 8(a), F.R.C.P., which requires that jurisdictions be shown in pleadings. Place an “X” in oneof the boxes. If there is more than one basis of jurisdiction, precedence is given in the order shown below.
United States plaintiff. (1) Jurisdiction based on 28 U.S.C. 1345 and 1348. Suits by agencies and officers of the United States are included here.
United States defendant. (2) When the plaintiff is suing the United States, its officers or agencies, place an “X” in this box.
Federal question. (3) This refers to suits under 28 U.S.C. 1331, where jurisdiction arises under the Constitution of the United States, an amendment to theConstitution, an act of Congress or a treaty of the United States. In cases where the U.S. is a party, the U.S. plaintiff or defendant code takes precedence, and box1 or 2 should be marked.
Diversity of citizenship. (4) This refers to suits under 28 U.S.C. 1332, where parties are citizens of different states. When Box 4 is checked, the citizenship of thedifferent parties must be checked. (See Section III below; federal question actions take precedence over diversity cases.)
III. Residence (citizenship) of Principal Parties. This section of the JS 44 is to be completed if diversity of citizenship was indicated above. Mark this sectionfor each principal party.
IV. Nature of Suit. Place an “X” in the appropriate box. If the nature of suit cannot be determined, be sure the cause of action, in Section VI below, is sufficientto enable the deputy clerk or the statistical clerks in the Administrative Office to determine the nature of suit. If the cause fits more than one nature of suit, selectthe most definitive.
V. Origin. Place an “X” in one of the seven boxes.Original Proceedings. (1) Cases which originate in the United States district courts.
Removed from State Court. (2) Proceedings initiated in state courts may be removed to the district courts under Title 28 U.S.C., Section 1441. When the petitionfor removal is granted, check this box.
Remanded from Appellate Court. (3) Check this box for cases remanded to the district court for further action. Use the date of remand as the filing date.
Reinstated or Reopened. (4) Check this box for cases reinstated or reopened in the district court. Use the reopening date as the filing date.
Transferred from Another District. (5) For cases transferred under Title 28 U.S.C. Section 1404(a). Do not use this for within district transfers or multidistrictlitigation transfers.
Multidistrict Litigation. (6) Check this box when a multidistrict case is transferred into the district under authority of Title 28 U.S.C. Section 1407. When this boxis checked, do not check (5) above.
Appeal to District Judge from Magistrate Judgment. (7) Check this box for an appeal from a magistrate judge’s decision.
VI. Cause of Action. Report the civil statute directly related to the cause of action and give a brief description of the cause. Do not cite jurisdictional statutesunless diversity. Example: U.S. Civil Statute: 47 USC 553
Brief Description: Unauthorized reception of cable service
VII. Requested in Complaint. Class Action. Place an “X” in this box if you are filing a class action under Rule 23, F.R.Cv.P.Demand. In this space enter the dollar amount (in thousands of dollars) being demanded or indicate other demand such as a preliminary injunction.Jury Demand. Check the appropriate box to indicate whether or not a jury is being demanded.
VIII. Related Cases. This section of the JS 44 is used to reference related pending cases if any. If there are related pending cases, insert the docket numbersand the corresponding judge names for such cases.
Date and Attorney Signature. Date and sign the civil cover sheet.
Case 2:14-cv-01102 Document 1-2 Filed 12/10/14 Page 2 of 2 PageID #: 16
