| 主权项 |
1. A planar optical waveguide circuit, comprising:
an optical waveguide modulator comprising:
an input waveguide configured to receive input light, anda modulator output waveguide configured to output modulated light; and an in-line optical waveguide tap configured to tap off a fraction of the modulated light for monitoring, the in-line optical waveguide tap comprising:
a multi-mode interference (MMI) coupler comprising first and second input ports and first and second output ports, andan unused waveguide that is directly coupled, at a first end, to the second input port of the MMI coupler and terminated, at a second end, in a first substrate to avoid picking up any stray portion of the input light or the modulated light propagating in the first substrate; wherein the modulator output waveguide is optically coupled to the first input port of the MMI coupler to receive the modulated light from the optical waveguide modulator, and the MMI coupler is configured to couple non-equal fractions of the received modulated light into the first and second output ports. |
