This system enables the basic properties of optical fibres to be investigated and the ideas then extended to demonstration of some of the principal scientific and commercial uses. The low-cost plastic fibre may be cut to any desired length with a sharp knife and does not require any special terminating devices. It is also completely non hazardous. The system comprises a transmitter, a receiver (both built onto P.C. boards 120mm x 150mm) and a 25m length of optical fibre. 20m of this is intended for speed of light determination and long distance communication demonstrations. Technical Specifications:. Transmitter:. Light source: High intensity red LED, output at 630nm. Modulation: Internal or external. The internal modulation source is a 300kHz oscillator (normally used for the speed of light experiment). External modulation input: 0 to 2V d.c. linear, up to 5V digital, or a.c. coupled via external capacitor (not supplied). External modulation frequency range: d.c. to greater than 300kHz, TTL compatible. Monitor output: 0 to 2.5V, for connection to an oscilloscope, or to measure the LED operating current. Power requirements: 5 to 6V smooth d.c., reverse polarity protected. Terminations, Optical: simple push in connection for 1mm diameter optical fibres. Terminations, Electrical: all connections by both 2mm and 4mm sockets. Receiver:. Input: Solid state photo-detector. Output 1: d.c. to greater than 5kHz, for connection to meters etc. and general analogue audio signals. Output 2: High speed digital output, 0 to 5V from below 20Hz to above 300kHz. Controls: Two, providing for zero-set and gain on output 1. Power requirements: 5 to 6V smooth d.c. reverse polarity protected, (the transmitter and receiver may share the same power supply if desired). Terminations, Optical: simple push-in connection for 1mm diameter optical fibres. Terminations, Electrical: all connections by both 2mm and 4mm sockets.
