PURPOSE: To reduce the size of a light signal transmitting unit by disposing a half mirror to one output of laser diodes which constitute a ray group.
CONSTITUTION: A CPU 21 applies a signal selection command to a modulation signal generating circuit 22 to generate a modulation signal. This modulation signal is branched to two signals in a branching circuit 23, one output of which is sent to a channel selection circuit 24. The other output of the circuit 23 is inputted directly to the laser diode (LD) 4, by which the light signal modulated in intensity by a modulation frequency is generated in the output of the diode LD 4. This light signal is branched to two signals by the half mirror 27, one of which is entered as a reference light signal via a reference light signal output terminal of the transmitting unit 20 to a reference fiber 61, the other is reflected by a prism 28 via optical switch groups 261W263 and is entered as a measuring light signal via a measuring light signal output terminal to a fiber 62 to be measured. The light signal of the laser diode is branched to two signals and the branched signals are used as the reference and measuring light signals in such a manner, by which the need for a light source to be exclusively used for generating the reference light signal is eliminated and the size of the unit is reduced.
TANIMOTO TAKAO
MIYAO HIDETOSHI
