The present invention even improve the communication speed of the uplink signal, to provide an optical beacon can be properly received the uplink signal.
A light receiving portion 11 of the optical beacon 4 of the present invention includes a low-pass filter circuit 42 for passing a signal of a frequency band lower than half the frequency of the fundamental frequency of the downlink signal, the base of the downlink signal a first trap circuit portion 40 for removing the signal around the frequency, and the second trap circuit 41 to eliminate the signal around half the frequency of the fundamental frequency of the downlink signal, by providing the, the light receiving part 11 is provided with a filter circuit 33 for removing the signal component of the downlink signal from the optical signal received.
.FIELD 4