OPTICAL DEVICE AND TRANSMITTER

摘要

PROBLEM TO BE SOLVED: To increase light-receiving power of a monitor while reducing a size thereof.SOLUTION: An optical device 100 has an optical waveguide 102 which is formed on a substrate 101 having an electro-optic effect and which comprises incident waveguides 102a, parallel waveguides 102b along electrodes 103, and emission waveguides 102c, where one of the pair of emission waveguides 102c is used as an output waveguide 102 for signal light so as to output the signal light to the outside, while the other is used as a monitor optical waveguide 102cb of the signal light. A light-receiving element 112 is disposed on the monitor optical waveguide 102cb. A groove 111 is formed in a substrate 101 portion of the monitor optical waveguide 102cb where the light-receiving element 112 is disposed. The monitor optical waveguide 102cb is formed in such a manner that a width W2 of the optical waveguide increases compared to a width W0 at a start side as the waveguide approaches the groove 111.