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HUAWEI TECHNOLOGIES CO., LTD.
Analysis of Multi-channel
Crosstalk with SOA as Pre-
amplifier in 100G EPON
Ting Yang, Dekun Liu
May, 2017
HUAWEI TECHNOLOGIES CO., LTD. 2
Background
Due to the lower receiver sensitivity at 25Gb/s line rate and the
extra loss of mux/demux, 100G EPON high likely needs optical
pre-amplifiers to meet the PR30 power budget requirement .
From both implementation and cost consideration, 4 channels of
100G share a same pre-amp SOA is a more practical solution.
Due to the fast carrier recovery time in SOA, when multiple
channels share a same SOA, some crosstalk between channels
will happen.
This contribution study the crosstalk effect between channels
when a shared pre-amp SOA is used for 100G EPON and shows
some initial experiment results.
HUAWEI TECHNOLOGIES CO., LTD. 3
Experimental setup
25G EML
Tx1
25G EML
Tx2
DATA1
DATA2D
EM
UX
Error
Detector
25G PIN/APD
Rx1
50:50
Coupler
DE
MU
X
Optical
power meter
Attenuator
Error
Detector
25G PIN/APD
Rx1
SO
A
50:50
Coupler
Electrical path
Optical path
Electrical path
Optical path
1294.6 nm, ER=8.5dB 1299.9 nm, ER=8 dB 1308.3 nm, ER=9.5dB
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Sensitivity of 25G APD & 25G PIN
-28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8
10
9
8
7
6
5
4
3
2
25G APD
25G PIN
-Lo
g1
0(B
ER
)
Received power [dBm]
Parameter Value Unit
Tx bit rate 25.78125 Gb/s
Tx wavelength 1294.6 nm
Tx output power 2 dBm
Tx ER 8.5 dB
Rx responsivity APD: 3~6
A/W PIN: 0.75
Rx sensitivity
(@BER=1E-3)
APD: -25.9 dBm
PIN: -17.2
Test conditions: back-to-back, NRZ, PRBS=2^31-1
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Transmission spectra of filter
CWDM Filter
LAN-WDM Filter
1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350-60
-50
-40
-30
-20
-10
0
10
No
rma
lize
d [d
B]
Wavelength [nm]
1290 nm
1288 1292 1296 1300 1304 1308 1312 1316-60
-50
-40
-30
-20
-10
0
10
No
rma
lize
d [d
B]
Wavelength [nm]
1295.56 nm
For input power of -25 dBm, crosstalk power of -9 dBm
For input power of -28 dBm, crosstalk power of -9 dBm
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Case1: 25G APD with CWDM filter
-32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12
10
9
8
7
6
5
4
3
2
w/o crosstalk
w crosstalk, -29 dBm
w crosstalk, -19 dBm
w crosstalk, -9 dBm
-Lo
g1
0(B
ER
)
Received power [dBm]
25G APD w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
Rx. Sen.
(@BER=1E-3) -25.9 dBm -29.8 dBm -29.5 dBm -29.3 dBm -25.3 dBm
25G APD ROSA, SOA 120mA 45degC
λ1 (test signal)
λ1
λ2
λ2 (crosstalk signal)
Pre-amp Rx
CWDM Demux
DE
MU
X
Error
Detector
25G PIN/APD
Rx1
DE
MU
X
Error
Detector
25G PIN/APD
Rx1SO
A
50:50
Coupler
1270 nm
1330 nm
1290 nm
1310 nm
HUAWEI TECHNOLOGIES CO., LTD. 7
Case2: 25G PIN with CWDM filter
-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10
10
9
8
7
6
5
4
3
2
w/o crosstalk
w crosstalk, -29 dBm
w crosstalk, -19 dBm
w crosstalk, -9 dBm
-Lo
g1
0(B
ER
)
Received power [dBm]
25G PIN ROSA, SOA 120mA 45degC
25G PIN w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
Rx. Sen.
(@BER=1E-3) -17.2 dBm -29.1 dBm -28.9 dBm -28.6 dBm -24.9 dBm
λ1 (test signal)
λ1
λ2
λ2 (crosstalk signal)
Pre-amp Rx
CWDM Demux
DE
MU
X
Error
Detector
25G PIN/APD
Rx1
DE
MU
X
Error
Detector
25G PIN/APD
Rx1SO
A
50:50
Coupler
1270 nm
1330 nm
1290 nm
1310 nm
HUAWEI TECHNOLOGIES CO., LTD. 8
Case3: 25G APD with LAN-WDM filter
-34 -32 -30 -28 -26 -24 -22 -20 -18
10
9
8
7
6
5
4
3
2
w/o crosstalk
w crosstalk, -29 dBm
w crosstalk, -19 dBm
w crosstalk, -9 dBm
-Lo
g1
0(B
ER
)
Received power [dBm]
25G APD ROSA, SOA 120mA 45degC
25G APD w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
Rx. Sen.
(@BER=1E-3) -25.9 dBm -31.7 dBm -31.4 dBm -31.2 dBm -28.5 dBm
λ1 (test signal)
λ1
λ2
λ2 (crosstalk signal)
Pre-amp Rx
LAN-WDM Demux
HUAWEI TECHNOLOGIES CO., LTD. 9
Case4: 25G PIN with LAN-WDM filter
-32 -30 -28 -26 -24 -22 -20 -18 -16 -14
10
9
8
7
6
5
4
3
2
w/o crosstalk
w crosstalk, -29 dBm
w crosstalk, -19 dBm
w crosstalk, -9 dBm
-Lo
g1
0(B
ER
)
Received power [dBm]
25G PIN ROSA, SOA 120mA 45degC
25G PIN w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
Rx. Sen.
(@BER=1E-3) -17.2 dBm -30.1 dBm -29.7 dBm -29.4 dBm -26.6 dBm
λ1 (test signal)
λ1
λ2
λ2 (crosstalk signal)
Pre-amp Rx
LAN-WDM Demux
HUAWEI TECHNOLOGIES CO., LTD. 10
Overview comparison
w/o SOA w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
25G APD
Rx. Sen.
(@BER=1E-3)
-25.9 dBm -29.8 dBm -29.5 dBm -29.3 dBm -25.3 dBm
25G PIN
Rx. Sen.
(@BER=1E-3)
-17.2 dBm -29.1 dBm -28.9 dBm -28.6 dBm -24.9 dBm
CWDM case
w/o SOA w/o crosstalk w. crosstalk
power of -29 dBm
w. crosstalk
power of -19 dBm
w. crosstalk
power of -9 dBm
25G APD
Rx. Sen.
(@BER=1E-3)
-25.9 dBm -31.7 dBm -31.4 dBm -31.2 dBm -28.5 dBm
25G PIN
Rx. Sen.
(@BER=1E-3)
-17.2 dBm -30.1 dBm -29.7 dBm -29.4 dBm -26.6 dBm
LAN-WDM case
HUAWEI TECHNOLOGIES CO., LTD. 11
Summary
When multiple channels share a same pre-amp SOA:
The crosstalk penalty for other channels is less than 1dB if
the input power of crosstalk channel is comparable with
that of the test channel.
If the input power of crosstalk channel is distinctly higher
than that of test channel (such as 20dB more), there will
be serious crosstalk penalty.
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Analysis:
The gain of SOA will decrease as the total input power increases.
In worst case, the total power of λ1,λ2,λ3 can be 24dB higher than λ4.
(14dB ODN dynamic range, 5dB ONU launch power spread range together
with log10(3) )
Such a big dynamic range in PON upstream will be the killer for the shared
pre-amp SOA used in OLT for upstream.
SOA Gain vs Input power
Gai
n
Bias current
If three strong signal together with one weak signal arrive the OLT at the same time, the SOA will become saturated and can’t provide enough gain for weak signal
HUAWEI TECHNOLOGIES CO., LTD. 14
It needs more SOA gain due to the insertion loss of Demux
For discrete components solution:
Cost is very high, size is very big, heat dissipation is vey challenging
For optical integration solution:
Narrow band filter is very difficult to design
Both filter and SOA must be polarization insensitive
Size and heat dissipation is very challenging
Technical maturity is poor
Solution (1)-single channel SOA
SOA filter Rx
SOA filter Rx
SOA filter Rx
SOA filter Rx
Dem
ux
Narrow band
It’s not a good solution for commercialization in foresee near term
HUAWEI TECHNOLOGIES CO., LTD. 15
Solution(2) –single domain DBA
All 4 sub-channels in a single scheduling domain
This will result in huge bandwidth wasting
guo_3ca_3_0516.pdf
HUAWEI TECHNOLOGIES CO., LTD. 16
Final thoughts:
There still be a lot of issues on the feasibility of
100G EPON pre-amp SOA to overcome the
needed power budget issue.
The task force need to decide which way we
should go or explore some more potential
solutions.