LiNbO₃ optical waveguide modulator for bidirectional transmission

Abstract

Abstract A new bidirectional external optical modulator using Fresnel reflection light has been proposed and developed. Since weak light reflected from the end of a crystal can be modulated in this modulator, no laser source is required if the modulator is intended for home use. This modulator also has no significant effect on a video signal in the downstream. In the external modulator designed for trial use, insertion loss was less than 3 dB, the half‐wave voltage was 10 V, and the half‐wave voltage difference and phase difference between the two modes were 2 percent and 5 degrees. A small module of the present device was created for use in a home optical terminal station of a demand access‐type Hivision CATV system. In this bidirectional transmission experiment, stable channel selection and good Hivision receiving image with C/N > 20 dB were confirmed. For the uplink 64 kbit/s NRZ signal, bit error rate (BER) of less than 10 −8 was obtained.