WAVELENGTH DIVISION MULTIPLEXING & CHROMATIC DISPERSION

Wavelength-division Multiplexing (WDM) is a method by which several wavelengths of light are carried in a single optical fibre. This allows for a multiplication in capacity, in addition to making it possible to perform bidirectional communication. Several Gbps signals are combined using WDM technique to utilize the vast bandwidth of fibre which is essential to meet the ever growing demand of communication.

Chromatic dispersion results from variation in the propagation delay with wavelength and is depending on the fibre material and dimension. Chromatic dispersion occurs due to the dependence of the velocity of light on the optical frequency when light propagates through the fibre. Different wavelength of light propagates at different velocity in a given medium whose effective index of refraction (neff) varies with respect to the wavelength of light. The first derivative of this delay versus wavelength is the chromatic dispersion value typically specified for fibre.

Benchmark WDM setup consists of individual modules in a vision to provide the users to gain knowledge on the building blocks of WDM and also enhances them to conduct various other experiments separately.

Benchmark WDM & CD teaches the characteristics of the key components used for WDM and CD study. It teaches the concept of wavelength division multiplexing and Chromatic dispersion measurement of single mode fibre. The study of the response of the photo detector at the receiver for the multiplexed wavelength gives a clear understanding of how the lights of two different wavelengths are combined in the fibre. The OFS WDM&CD setup includes a signal generator which gives out two identical signals having a fixed delay between them to facilitate better observation of WDM concept. The knowledge of chromatic dispersion is essential for students while designing high speed fibre optic communication system with dispersion compensation.

List of Items

LD Modulator - FOTX-610	-	2 nos
LD Unit (1310nm & 1550nm) FOSM-U900 & FOSM-U1000	-	1 each
Receiver - FORX-500	-	2 nos
LD Driver - FOSM-D600	-	1 no
WDM Coupler	-	2 nos
Fixed Attenuators - 1310nm & 1550nm	-	1 each
TTL Generator - TTL GENV1.0 1	-	1 no
Single mode Patch cords	-	5 nos
2.5 km fibre spool	-	1 no

Specifications

Laser diode unit 1550 nm

Type : Fabry Perot
Wavelength : 1550nm
Output power after 1m single mode fibre : -5 dBm
Max Output power : 2mW
Max current : 30mA
Optical output connector : SC receptacle

Laser diode unit 1310 nm

Type : Fabry Perot
Wavelength : 1310nm
Output power after 1m single mode fibre : -5 dBm
Max Output power : 0.9mW
Max current : 40mA
Optical output connector : SC receptacle

Wavelength selective coupler (WDM)

Operating wavelength :1310/1550nm ± (10nm)
Insertion loss :1dB typical
Ratio :1:1

FOSM - D600: LD driver

Possible modes of operation :Forward bias
Bias Control :Potentiometer
Bias Voltage variation :10V max
Power Supply :10V DC
Interface Connectors :
- LD Unit - 5x2 Header
- Power supply - 5 pin DIN - DIN

FOTX – 610 - LD Modulator

TTL Input Data Rate :
- 400Kbps to 34Mbps NRZ
- 200Kbps to 17Mbps RZ
Power Supply :+ 5V DC
Interface Connectors :
- TTL I/P - BNC
- LD Unit - 5x2 Header
- Power supply - 5 pin DIN - DIN

FORX – 500 - Optical Receiver

Incident optical wavelength :1550nm
Data output :TTL & Direct Amplifier output
Modulated optical data input rate :
- 100Kbps to 34 Mbps for NRZ
- 100Kbps to 17 Mbps for RZ
Power supply :+ 5V DC
Interface connectors :
- Optical Input - ST
- TTLOutput - BNC
- Direct Amplifier output - BNC
- Power supply - 5 pin DIN-DIN

TTL Gen

Type :Button press
Clock speed :564 kHz
Patterns :
- 2 TTL signals without delay
- 2 TTL signals with 420 ns delay
Power supply :+ 5V DC
Interface connectors :
- TTL Output - BNC
- Power supply - 5 pin DIN-DIN

Fibre patch cords

Type :Single Mode Fibre
Length :1m, 2.5 km (for CD experiment)
Core diameter :8µm
NA :0.12
Connector :SC/APC

*Specifications subject to change without notice

List of Experiments

Study of Characteristics of Laser Diode
Measurement of Isolation and Insertion loss of WDM coupler
Study of WDM concept
WDM – End-to-End operation
Study of Chromatic Dispersion effect