INTRODUCCION A FIBRAS OPTICASSEMINARIO DE CERTIFICACION
MEXICO 2001
Conceptos Básicos
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Historia
1704 Isaac Newton publica “Treatise of Optics” sobre la refracción
de la luz.
1850s Se demuestra “La Reflexión Total interna”
1880 Se patenta el concepto “Luz entubada”
*
NOTES: In the mid 1800s a British physicist named John Tyndall
demonstrated that light could be kept inside a stream of water. He
would place a glass jar with a spout at the bottom on a table and
shine a light into the jar along the same axis as the spout. The
light would stay inside the water stream until the stream broke
apart near the bottom. Tyndall had demonstrated the principle of
“total internal reflection”.
In 1880 an engineer named William Wheeler patented a scheme that he
thought could “pipe” light through homes and buildings. He made
tubes that had a shinny surface on the inside and connected them in
the same way that water pipes are connected. He placed a bright
light at the beginning of the pipe system and focused the light
into the tube. His method was not very efficient, but variations of
his idea eventually led to optical fibers.
In the 1950s, Brian O’Brien Sr. of the United States and Harry
Hopkins and Narinder Kapany, both from England, worked on a refined
concept that used two concentric “layers” of glass with the inner
layer having a higher “index of refraction” than the outer layer.
In this configuration, the glass could bend and still carry light
to the other end. The term “fiber optics” started to be used during
this time. O’Brien made bundles of the fibers and used them to
transmit light for use in the medical and inspection fields.
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Entrando a la era de la Fibra Óptica
1960 Primer Láser
1970 Fabricación de fibra mono-modo con atenuaciones menores a 20
dB/km
1977 Primer sistema comercial en servicio
1997 Se desarrolla el conector VF-45
1998 Aparecen comercialmente las primeras fuentes VCSEL
*
NOTES: In 1960, a major development occurred that opened the way
for advances in fiber optic communications systems. Theodore H.
Maiman demonstrated the first working laser. A laser produces a
narrow beam of light that can be coupled to a fiber optic strand.
This gave the fiber optic systems a greater distance of
operation.
In 1970, a breakthrough in fiber optic manufacturing technology was
achieved. Scientists at the Corning Glass Works were able to make
fiber optic strands that had a loss of less than 20 dB/km. At one
time 20 dB/km was thought to be the theoretical limit of the
glass.
In 1977, the first commercial long distance system went into
operation.
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ISO 11801
ANSI/EIA/TIA 568A
TSB 75
*
NOTES: In 1960, a major development occurred that opened the way
for advances in fiber optic communications systems. Theodore H.
Maiman demonstrated the first working laser. A laser produces a
narrow beam of light that can be coupled to a fiber optic strand.
This gave the fiber optic systems a greater distance of
operation.
In 1970, a breakthrough in fiber optic manufacturing technology was
achieved. Scientists at the Corning Glass Works were able to make
fiber optic strands that had a loss of less than 20 dB/km. At one
time 20 dB/km was thought to be the theoretical limit of the
glass.
In 1977, the first commercial long distance system went into
operation.
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Estándares EIA/TIA
¿Qué es una Fibra Optica?
Podemos considerarla como una guía de onda dieléctrica, es decir es
un tubo de vidrio maciso muy pequeño, en dos capas, integrada por
un núcleo y un revestimiento. El principio de operación de basa en
los fenómenos de reflexión y refracción de la luz.
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El efecto del índice de Refración en la Fibra Óptica
El índice de Refracción indica la relación de la velocidad de la
luz en el vacío.
Revestimiento
Núcleo
n2
n1
n2
*
Fiber optics is not difficult to understand. It’s as simple as
light bouncing down a pipe (although fiber is made of a solid piece
of glass). The basis of fiber optic communication is optical fiber,
a thin, flexible waveguide through which light is
transmitted.
A fiber optic strand is made of two components called the core and
the cladding. Light enters the fiber, bounces down the core and
exits at the opposite end.
How does this work? Well, the core has a different index of
refraction than that of the cladding (about 1%). When the light
that enters the core comes to the core/cladding boundary (and since
the cladding has a lower refractive index) it will be bent away
from the cladding and back into the core. This process is called
total internal reflection.
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Elementos de la fibra
Características y ventajas de la Fibra Óptica
No conductiva
No RFI/EMI
Seguridad
*
NOTES: Non-conductive - Fiber strands do not conduct electricity
and are therefore not subject to overvoltage situations
No RFI/EMI - There is no induction between fibers to cause
interference
No ground loop - Copper cable system could loop through earth
ground, but light signals through fiber is not subject to
grounding
Data security - There is no electro magnetic radiation and tapping
the line is difficult at best.
Greater data capacity - Fiber transmissions have been tested at
over 20 gigabits
Lower installed cost - With new technology it is becoming feasible
to install fiber optic systems
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Espectro Electromagnético
Rayos Cósmicos
RAyos Gama
Rayos X
*
NOTES: When working with light rays it is more common to specify
the wavelength of the light. Visible light is only a small portion
of the electromagnetic spectrum. We can see light rays that range
from 400 to 700 nanometers (nm). The color of the light we see can
be specified by its’ wavelength. Red is in the range of 660nm,
green is in the range of 500nm and blue is in the range of
470nm.
Wavelength is calculated using the speed of light in free space
divided by the frequency of the wave being measured. By using this
formula we find that the wavelength of a typical power outlet in
the home (60 Hz) is equal to 3,100 miles. As you can see, the
frequency and the wavelength of a signal are inversely
proportionate. As the frequency goes up, the wavelength goes
down.
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Propiedades de la Luz
Reflexión - Los rayos rebotan en la interfase.
Refracción - Los rayos de luz se desvían al pasar por la
interfase.
Rayo Incidente
Rayo Reflejado
Rayo Refractado
Índice de Refracción
Índice de Refracción=
*
The index of refraction is the ratio of the speed of light in a
vacuum to the speed of light in a material. The material must be
transparent enough to pass some light through it. Light always
travels through a vacuum faster than through a material, therefore,
the index of refraction will always be greater than 1.
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Indice de refracción*
Cable de Fibra Óptica(SM) 1.471
Vidrio 1.5-1.9
Diamante 2.42
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Aceptación de la Luz en la Fibra
Cono de Aceptancia
N.A. (Apertura Numérica)
*
Light entering the core must do so within a certain acceptance cone
(shaped like a funnel) to achieve the total internal reflection.
The larger the cone, the easier it is to couple light into the
fiber. This cone can be described by a mathematical formula and the
result is called the “Numerical Aperture” (NA). The acceptance
angle of the air to fiber interface is normally much greater than
that of the core to cladding interface. Because light striking the
core to cladding interface at an angle greater than the critical
angle is lost through the cladding, it is important to use the
critical angle of this interface for the acceptance cone.
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Pulso Eléctrico de entrada = Pulso Eléctrico de salida
Conversión
Eléctrica
Concepto Básico de la Transmisión de luz por fibra óptica
Pulso de Luz
*
This is a simplified fiber optic communication system. An
electrical pulse is used to trigger an LED generating a light pulse
which is injected into the fiber. The detector senses the light
pulse and generates a small electrical pulse which is amplified,
formatted and presented at the output. The output pulse is the same
as the input pulse, as if the fiber link had not even been
there.
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Clasificación de las Fibras Opticas
Multimodo
*
Comparison of 3 core sizes: 200um for industrial communications
such as PLC’s, 62.5um for local area networks, and 9um for long
distance telecommunications and CATV.
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Fibra Multi Modo con perfil de índice escalonado
Fibra con índice escalón
*
There are 2 types of fiber, single mode and multi-mode. Multi-mode
means that there are multiple paths (or modes) for the light to
travel down the fiber. The larger the core, the more modes it will
carry. A 100um core will carry 5744 modes at 850nm.
Multi-mode fibers are either step-index or graded-index. Step-index
fibers have a distinct difference (a step) in the core’s and
cladding’s index of refraction.
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Dispersión Modal
La luz viaja a través de varias trayectorias (modos)
El tiempo de propagación de los modos varía de acuerdo a la
longitud de la trayectoria
Núcleo de la fibra
Fibra Multi Modo con perfil de índice graduado
Fibra Multi Modo con índice graduado
Perfil del índice de refracción
*
The change in index of refraction between core and cladding in a
graded-index is gradual. The index is highest in the center of the
core and decreases towards the outer edge.
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Fibra Monomodo
Pulso de salida
Pulso de entrada
*
Single mode fiber is a step index fiber. It too has a distinct
difference between the core and claddings index of refraction. This
type of fiber has a core that is about 10um in diameter.
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Atenuación
Es el decremento de la potencia de una señal óptica desde la
entrada hasta la salida.
Entrada
Salida
*
In copper systems we have loss which is called resistance. We
measure resistance in ohms.
In fiber we have loss. We call this loss (or decrease in power)
attenuation which we measure in dB (decibels). The lower the
attenuation, the more light that is transmitted.
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Pérdidas de luz
Se mide en decibeles(dB)
10 dB = 10% Transmisión de Luz
20 dB = 1% Transmisión de Luz
Input Light
Output Light
*
3dB of loss means that you have lost 50% of the light that you’ve
started with.
Example: if you have a 100 watt light bulb and have 3 dB of loss
you end up with 50 watts of light. If you take that 100 watts and
have 6 dB of loss you have 25 watts left ( 50% of 100 watts is 50
watts (the first 3dB) and 50% of 50 watts is 25 watts (a second 3dB
for a total of 6dB).
100 watts
Causas de Atenuación
Attenuation of the light can be caused by several factors:
1. Absorption of the light by materials in the glass.
2. Scattering of the light out of the core due to impurities.
3. Leakage of light out of the core due to exceeding the maximum
bend radius of the fiber optic strand. This is called a macrobend.
Once the light leaves the core, it is absorbed in the
cladding.
4. Microbends (high attenuation due to pin-point pressure). This
can happen when water surrounds the fiber and then freezes.
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Radio Mínimo de Curvatura
Exceder el Radio Mínimo de Curvatura implica tener Atenuación
debido a las Macrocurvaturas.
Dispersión de guia-onda
*
Exceeding the minimum bend radius can cause 2 problems. The first
is catastrophic failure (breaking of the fiber).
The second is increased loss. When you bend a fiber to tightly the
light in the core leaks out into the cladding.
DEMO: use the 7XE-660 visible light source and bend some fiber till
you see the red light “leaking” out.
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Atenuación
Atenuación
Fuentes de Luz
Bajo Costo
Baja Potencia
Bajo Costo
Potencia Media
*
There are 2 types of light sources used in fiber optics, LED’s
(used for multi-mode) and lasers (used for single mode).
Light Emitting Diode (LED) - This is an inexpensive semiconductor
device that will produce light using a small electrical current to
release photons from certain semiconductor materials. The selection
of the material determines the wavelength or color of the light.
The bandwidth of the light is relatively wide. The amount of output
power from the LED is small. The physical size of an LED is much
larger than the core of a fiber optic strand. An LED should have a
useful life of over 100, 000 hours.
Laser Diode - An expensive semiconductor device that produces a
coherent beam of light when stimulated with the proper electrical
signals. The selection of materials and the stimulating electrical
signals determine the wavelength or color of the light. The
bandwidth of the light can be very narrow, sometimes only 1 um
wide. The output window of the laser diode is the same size as the
core of a fiber optic strand. The amount of output power that can
be transferred from the laser diode to the core is much greater
than an LED.
Fiber optic strands made of silica have some attenuation at 850 nm,
low attenuation at 1300 nm and even lower attenuation at 1550 nm.
LEDs can be made to have a relatively high output at 850 nm and
1300 nm while laser diodes can be made to have a high output at all
three wavelengths.
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LED vs Laser
*
This is a representation of the spectral characteristics of an
output device such as a Laser or LED source. It shows the Central
Wavelength and the Spectral Width of the device. LED’s have a
Spectral Width of about 50nm to 200nm. This means that the maximum
or peak power is comprised of light from within a this portion of
the spectrum combined together. Laser’s on the other hand have a
very narrow spectral width and the peak power comes from a narrower
more concentrated spectrum of light. Photodyne provides this
information with every light source shipped.
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Dispositivos Receptores
Foto Diodo de Avalancha:
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Detectores
500
700
900
1100
1300
1500
1700
0.00
0.20
0.40
0.60
0.80
Sensibilidad
500
700
900
1100
1300
1500
1700
Cables
de
CABLES DE FIBRA ÓPTICA
CABLE DE TUBO APRETADO
Tipos Básicos de Cable (Comparación)
TUBO APRETADO= El tubo separador es extruído directamente sobre la
Fibra (900 MICRAS)
*
Cables de tubo holgado
Construcción del Cable
Chaqueta externa (PVC)
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Construcción del Cable
Selección del cable adecuado
¿Qué criterios debo seguir?
Cobre
Fibra Óptica
Clasificación del Cable
- Emitido cada 3 años por la NFPA
- En 1987 NEC requirió que todos los cables de fibra cumplieran
cierto nivel de seguridad contra el fuego.
- Es sólamente un recomendación - Artículo 770 : Cable de Fibra
Óptica
UL - Underwriters Laboratory
- Se designana OF: Fibra Óptica
- OFC : Fibra Óptica Conductivo
- OFNR : Riser - Prueba UL 1666
- OFNP : Plenum - Prueba NFPA 262 - 1985
- Cable libre de Halógenos
3Telecom Systems Division
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Clasificación del Cable
La NEC 1987 requiere que todos los cables de fibra óptica deben
cumplir con cierto nivel de seguridad contra el fuego. Un cable
completamente dieléctrico se designa OFN (fibra óptica
no-conductivo) contrario a un OFC (fibra óptica conductivo). El
cable OFN es de aplicación general. Debe pasar la Prueba de Flama
en Charola Vertical UL 1581.
OFNR (fibra óptica no-conductivo riser) implica que todo miembro
dieléctrico del cable de fibra esté clasificado como “riser”. Un
riser es una charola o hueco vertical por el que corre el cable de
piso a piso dentro de un edificio. Los cables riser deben poseer
“características resistivas al fuego capaces de prevenir la
expansión del fuego de un piso a otro” Los cable riser deben pasar
las pruebas UL 1666. (más estricta que la UL 1581)
3Telecom Systems Division
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Clasificación del Cable
OFNP (Fibra óptica no-conductivo plenum) implica que todo miembro
dieléctrico del cable de fibra óptica esté clasificado como
“plenum”. Plenum es el espacio usado para el manejo del aire
acondicionados. El cable Plenum debe tener “características
adecuadas de resistencia al fuego y baja producción de humos”. Los
cables plenum deben pasar la prueba NFPA 262-1985 test, la cual es
la más estricta de todas la pruebas UL para cable. Los cables
plenum se prueban para características de humo y flama, pero no
para emisiones tóxicas.
3Telecom Systems Division
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Aplicaciones
Atado Aéreo
Instalación Vertical
Directamente Enterrado
Se recomienda cable de tubo apretado (Breakout o tight
buffer)
Evitar aplastar, enrollar y curvaturas cerradas.
Los procedimientos de instalación son los mismos que los de cable
eléctrico.
Cubiertas tipo OFNP o LSZH
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Ambientes del Cable
Instalación similar a los cables eléctricos soportados por una
guía.
Se recomienda tubo holgado debido al severo medio ambiente y
temperatura.
La mayoría de los tubos holgados pueden ser engrapados cada 3 a 5
pies, sujetados con cinchos o atados helicoidalmente.
Opción de cable autosoportado
Atado Aéreo
Instalación Vertical
Directamente Enterrado
Ambientes del Cable
Se requiere engrapado:
3 - 5 pies exteriores
50 - 100 pies interiores
La migración de las fibras en tubo holgado puede ser reducida
colocando lazos de 1 a 1.5 pies en lo alto, en el fondo y al
centro.
Cuniertas tipo OFNR o LSZH
Uso de Fire Barriers
Atado Aéreo
Instalación Vertical
Directamente Enterrado
Ambientes del Cable
El Cable se puede colocar directamente enterrado.
Se recomienda cable armado por el severo medio ambiente, roedores y
rocas.
Accesorios de localización
Atado Aéreo
Instalación Vertical
Directamente Enterrado
Comparativos
Diámetro Mayor Menor
Resistencia al impacto Baja Alta
Resistencia al triturado Baja Alta
Cambio de atenuación a baja
temperatura Bajo Alto
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CONECTORES DE FIBRA OPTICA
Conectores de Fibra Optica
Los conectores de fibra óptica son dispositivos diseñados para
proporcionar una unión mecánica, temporal, confiable y de bajas
pérdidas de dos extremos de fibra óptica o de un extremo de fibra
óptica con algún dispositivo fotoelectrónico.
3 Telecom Systems Division
*
NOTES: In the mid 1800s a British physicist named John Tyndall
demonstrated that light could be kept inside a stream of water. He
would place a glass jar with a spout at the bottom on a table and
shine a light into the jar along the same axis as the spout. The
light would stay inside the water stream until the stream broke
apart near the bottom. Tyndall had demonstrated the principle of
“total internal reflection”.
In 1880 an engineer named William Wheeler patented a scheme that he
thought could “pipe” light through homes and buildings. He made
tubes that had a shinny surface on the inside and connected them in
the same way that water pipes are connected. He placed a bright
light at the beginning of the pipe system and focused the light
into the tube. His method was not very efficient, but variations of
his idea eventually led to optical fibers.
In the 1950s, Brian O’Brien Sr. of the United States and Harry
Hopkins and Narinder Kapany, both from England, worked on a refined
concept that used two concentric “layers” of glass with the inner
layer having a higher “index of refraction” than the outer layer.
In this configuration, the glass could bend and still carry light
to the other end. The term “fiber optics” started to be used during
this time. O’Brien made bundles of the fibers and used them to
transmit light for use in the medical and inspection fields.
Volition Network Solutions
Consideraciones de los Conectores
Pérdida o pérdida de inserción; pérdida por mal empatado
Típicamente pérdida menor a 0.2 dB por par empatado (5% de pérdida
de señal)
Tipo de contacto: Recto, PC y Angulado
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Connection Loss Factors
Connection Loss Factors
Excentricidad
Núcleo-revestimiento
5.bin
Alineación Triaxial
Componentes Concéntricos
Componentes Longitudinales
Presión del resorte
Alineamiento de férulas
Tolerancias en las Pérdidas de Luz
Fibras con D.E. de 125 micras y 5 micras mal alineadas.
Núcleo multi modo de 50 micras –
Pérdida aceptable
Pérdida no aceptable
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Desplazamiento de Alineamiento Transversal
Desplazamiento en la Alineación Angular
Desplazamiento Angular (en grados)
Desplazamiento de Alineación Longitudinal
Con Gel
Consideraciones de los Conectores
Recto, PC, Angulado
Pérdidas de retorno
Consideraciones de los Conectores
Calidad del Pulido
Proceso de Pulido
Desbastar la Fibra
MM.- Manual
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Pulido de conectores
Oxido de Aluminio
Conectores de Fibra Optica
*
NOTES: In 1960, a major development occurred that opened the way
for advances in fiber optic communications systems. Theodore H.
Maiman demonstrated the first working laser. A laser produces a
narrow beam of light that can be coupled to a fiber optic strand.
This gave the fiber optic systems a greater distance of
operation.
In 1970, a breakthrough in fiber optic manufacturing technology was
achieved. Scientists at the Corning Glass Works were able to make
fiber optic strands that had a loss of less than 20 dB/km. At one
time 20 dB/km was thought to be the theoretical limit of the
glass.
In 1977, the first commercial long distance system went into
operation.
Volition Network Solutions
Conectores de Fibra Optica
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Conectores de Fibra Optica
Tendencia al desuso
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Conectores de Fibra Optica
Soluciones de Conectorización 3M
Soluciones de Conectorización
Soluciones de Conectorización
Reutilizable
Soluciones de Conectorización
No requiere adhesivos
Soluciones de Conectorización
No se requieren de instalaciones eléctricas
Ideal en aplicaciones de seguridad
Aplicaciones de alta densidad
VOL-0799
Empalmes de Fibra Óptica
Empalme por Fusión
• Se alinean las fibra y son fusionadas por un arco eléctrico en la
unión.
• Bajas pérdidas, típicamente para núcleos pequeños de fibras mono
modo.
• No se require adhesivos epóxicos.
• Equipo de alto costo.
Fibrlok II
Fibrlok II
Herramienta para Empalmes Mecánicos
Procedimiento simplificado de empalme, no requie entrenamiento
especial
Desempeño y Confiabilidad probada
3 Telecom Systems Division
FibrMax
8400
Familia 8400.
Diferentes tipos de conectores
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Standard
TOP
‘‘Economic’’
ONE
PROPTIC : Precabling Circular Frame System
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Cierres de Empalme
Fibra Óptica
Reintervenibles
Fibra Óptica
Sellado perfecto
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FibrDome
Reintervenible
o gabinete
Standard
MPE/O
BPE/O
Building Interface Boxes
METODOS
DE
PRUEBAS
Pruebas de Fibra Optica
Pruebas de pérdidas por inserción (Mediciones de potencia óptica)
OPM
Pruebas de retrodispersión o reflectometría (OTDR)
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Prueba de continuidad
Probador de luz intermitente
Usado para verificar que la luz pasa a través de la fibra
(continuidad punta a punta)
Se usa para la identificación de fibras
Verificar polaridad en sistemas duplexVerify polarity in a duplex
circuit
Esta prueba es úsitl sólo para pruebas fallas sencillas
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Pruebas de pérdidas por inserción
Atenuación
Se realiza utilizando una fuente de luz y un medidor de
potencia
Se mide la cantidad de pérdida de señal a lo largo de un enlace de
fibra
Medido en dB
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Prueba de atenuación
Proceso de dos pasos
Toma de Referencia (calibración)
Referencia (Calibración)
Paso 1
Considerelo como Cero de referencia
Power Meter
Light Source
Prueba del canal
Atenuación total= P2 - P1
Prueba de atenuación
Atenuación Aceptable
Fibra multimodo
Método de retrodispersión
Principios Básicos (OTDR)
OTDR
*
Principios Básicos del OTDR
Verificando el desempeño del sistema
Ocho pasos para analizar el desempeño
1. Calcular las pérdidas de la fibra
2. Atenuación en conectores
3. Pérdidas por empalmes
Switches Bypass
6. Determinar las pérdidas totales de potencia
7. Calcular el presupuesto de pérdidas
*
Verificando el rendimiento del sistema
Atenuación
Pérdidas en la fibra a la longitud de onda de operación
La atenuación del cable de fibra se expresa en dB/km
1.5 dB/km X 1.5 km = 2.25 dB
Determine las pérdidas por conectores
1.0 dB por par conectado
Pérdidas por empalmes
Atenuación
Verificando el desempeño
Determine la ganancia del sistema
Promedio de potencia del transmisor- sensibilidad del
receptor
(-18.0 dB) - (-31.0 dB) = 13.0 dB
Determine pérdidas de potencia (2.6 dB)
Margen de operación - use 2.0 dB
Pérdidas en el receptor - si no están establecidas, considere 0.0
dB
Margen de reparación - 2 empalmes a .3 dB = .6 dB
Presupuesto de enlace - Ganancia del sistema - Pérdidas de
potencia
13.0 dB - 2.6 dB = 10.4 dB
*
Verificando el rendimiento
Menos
Margen de desempeño del sistema 2.25 dB
*
Verificando el desempeño
Ancho de Banda
Expresado en Mhz
Velocidad de transmisión máxima para operar el sistema sin traslape
de pulsos de luz que produzcan BER
Debe ser >= ancho de banda del sistema
*