Optical Fibre & Digital Communication Training System (OFT)

oft-logo02 The Benchmark Optical Fibre & Digital Communication Training System – OFT – is a powerful, versatile and cost-effective experimenter kit ideal for training purposes at all levels and was developed in a joint effort by IIT-Madras and Benchmark Electronic Systems. The first trainer kit was built in 1988. Over the years, as per feedback from faculty all over the country, new versions were developed and built. Currently, the OFT is in its fourth version.

OFT - Features

oft-logo02 The Benchmark Optical Fibre & Digital Communication Trainer – OFT – is the base-line for every fibre optic laboratory. It demonstrates state-of-the-art concepts in fibre optic communications. It provides for easy experimentation and effectively bridges the gap between a leading-edge technology and currently available technical training tools. As the concepts demonstrated are no different from those encountered in real-life systems, it can provide significant insights, of direct relevance, to the student and practicing engineers alike. In addition, it can serve as a ready-made communications platform for photo typing and in applications calling for fibre optic capabilities.


  • Eleven usable 64 kbps channels
  • User definable frame marker (two alternating 8-bit markers - can be set to CCITT compatible)
  • On-board two digitised voice channels, one 8-bit data channel and several user-expansion channels
  • Demonstrates fully operational integrated voice/data fibre-optic communication link
  • RS - 232C communications module optional - demonstrates computer communications over fibre
  • Time Division Multiplexing of voice, data & user-defined data streams
  • Modular design enables configuration with user-defined modules
  • Wide scope for experimentation through use of external circuitry interfaced to kit
  • Comprehensive manual describes wide range of experiments - can form basis of courses
  • Ready -to -use kit comes complete with accessories




850nm and 650nm fibre links
Demonstrates established digital communication techniques such as:

  • Time Division Multiplexing, Transmitter & Receiver operation
  • PCM voice coding (at 64 Kbits/sec)
  • Manchester coding/decoding for timing recovery, etc.

Channels switchable at transmitter & receiver using time-switching principles
Easy interface to external circuitry - all required inputs and outputs provided and extensively documented
Power available to external circuitry as well
Comprehensive laboratory manual

  • clearly explains the theory of fibre optic analog and digital communications through in-depth experiments


  • all accessories required to conduct basic experiments and to interface to external circuitry are provided in the kit


  • RS-232C communication interface module available as option to enable computers to be connected over fibre - demonstrates integrated voice/data/RS-232 communication link.

OFT - Experiments


Basic Experiments
Can be done using just the standard kit
Fibre optic experiments

  • Fibre optic analog links
  • Digital links
  • Losses in optical fibre
  • Effect of EMI interference
  • Numerical aperture measurement

Multiplexing and digital communication experiments

  • Time division multiplexing
  • Framing in time division multiplexing
  • Manchester coding/decoding - timing recovery
  • Voice coding - A-Law
  • Pulse broadening in fibre optic communications

Advanced Experiments
Concepts explained in manual, requires circuit development by user

  • Interfacing 8kbps synchronous channels
  • Interfacing 64 kbps synchronous channels
  • Interfacing 256 kbps synchronous channels
  • Interfacing synchronous channels at less than 8 kbps
  • Asynchronous channel interfacing using over sampling
  • Asynchronous channel interfacing using stuffing

Advanced Applications
Concepts explained in manual, requires circuit development by user.

  • 1/4 voice channel
  • Manchester coder/decoder with PLL clock recovery
  • 4B/5B (or5B/6B) coder/decoder with clock recovery
  • Frame marker coder/decoder
  • RS-232 communication link
  • Slow-scan video link

OFT – Specifications


Number of channels 12 (64 Kbits/sec) channels, including one slot for 16 bit marker
Frame marker Two 8 bit markers in alternate frames, user settable, can also be set to CCITT standard
Coding/decoding Manchester coding/decoding
Data Rate 768 Kbits/sec, 1.536 Mbits/sec after Manchester coding
Voice PCM channels Two. (Two telephone handsets provided)
Voice coding A-Law
Analog input voltage 1V(pp)
Analog input bandwidth 100 KHz
Wavelengths 650nm and 850nm
FWHM spectral width 100nm
Fibre 1000 micron plastic fibre (1m, 3m and 20m lengths included)
Max link length 30m for 650nm optical digital link , 5m for 850nm link
Max data rate 2 Mbits/sec (NRZ)

*Specifications subject to change without notice

OFT – Ordering Information

Ordering Information

Description Part #
Optical Fibre and Digital Communication Trainer OFT
RS-232C Interface Module for OFT OFT RS-232C
20m (650nm) link option for OFT OFT-LINK-20

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