Optical modules having an improved optical signal to noise ratio

Abstract

Consistent with the present disclosure, a photonic integrated circuit (PIC) is provided that has 2 N channels (N being an integer). The PIC is optically coupled to N optical fibers, such that each of N polarization multiplexed optical signals are transmitted over a respective one of the N optical fibers. In another example, each of the N optical fibers supply a respective one of N polarization multiplexed optical signals to the PIC for coherent detection and processing. A multiplexer and demultiplexer may be omitted from the PIC, such that the optical signals are not combined on the PIC. As a result, the transmitted and received optical signals incur less loss and amplified spontaneous emission (ASE) noise. In addition, optical taps may be more readily employed on the PIC to measure outputs of the lasers, such as widely tunable lasers (WTLs), without crossing waveguides.

What is claimed is: 
     
         1 . An optical device, comprising:
 a substrate;   a plurality of lasers provided on the substrate;   a plurality of first optical hybrid circuits, each of which receiving a first portion of light output form a corresponding one of the plurality of lasers, the first plurality of optical hybrid circuits being provided on the first substrate;   a plurality of second optical hybrid circuits, each of which receiving a second portion of the light output from said corresponding one of the plurality of lasers, the second plurality of hybrid circuits being provided on the first substrate;   a plurality of first waveguides, each of which being optically coupled to a respective one of the plurality of first optical hybrid circuits, each of the plurality of first waveguides extending to an edge of the substrate and being optically coupled to a respective one of the first plurality of optical hybrid circuits;   a plurality of second optical waveguides, each of which being optically coupled to a corresponding one of the plurality of second optical hybrid circuits, each of the plurality of second waveguides extending to the edge of the substrate and being optically coupled to a respective one of the plurality of second optical hybrid circuits;   a plurality of variable optical attenuators provided on the substrate, each of which receiving a third portion of the light output from a corresponding one of the plurality of lasers;   a multiplexer that has inputs coupled to each of the plurality of variable optical attenuators, each of the variable optical attenuators selectively supplying at least a portion of the third portion of the light of a respective one of the plurality of lasers to a corresponding input of the multiplexer;   a receiver circuit, that receives an output from the multiplexer; and   a control circuit coupled to the receiver circuit, the control circuit adjusting a wavelength of each of the first plurality of optical signals based on outputs of the receiver circuit.   
     
     
         2 . An optical device in accordance with  claim 1 , wherein the plurality of lasers is a plurality of first lasers, the optical device further comprising a second laser provided on the substrate, the second laser supplying light, at least a portion of which is provided to the multiplexer, such that the light output by the second laser is received by the receiver circuit. 
     
     
         3 . An optical device in accordance with  claim 1 , wherein the control circuit further adjusts the wavelength of each of the first plurality of optical signals based on an output of the receiver circuit. 
     
     
         4 . An optical device in accordance with  claim 1 , wherein the plurality of lasers is a plurality of first lasers, and the control circuit is a first control circuit, the optical device further including:
 a second laser provided on the substrate, the second laser supplying light, a first portion of which is received by the receiver circuit; and   a second control circuit that receives a second portion of the light output from the second laser, the second control circuit adjusting a wavelength of the light supplied by the second laser based on the second portion.   
     
     
         5 . An optical device in accordance with  claim 4 , wherein the second control circuit is provided off the substrate. 
     
     
         6 . An optical device in accordance with  claim 4 , wherein the second control circuit includes an etalon. 
     
     
         7 . An optical device in accordance with  claim 2 , wherein the second laser is a distributed feedback (DFB) laser. 
     
     
         8 . An optical device in accordance with  claim 1 , wherein the receiver circuit includes:
 a delay line interferometer provided on the substrate, the delay line interferometer including a third waveguide and a fourth waveguide, the third waveguide having a longer optical length than the fourth waveguide;   a splitter having an input that receives said at least a part of the third portion of the light output from a respective one of the plurality of lasers, and first and second outputs, the first output of the splitter being coupled to a first end of the third waveguide and the second output of the splitter being coupled to a first end of the fourth waveguide;   a third optical hybrid circuit having first and second inputs, the first input of the third optical hybrid circuit being coupled to a second end of the third waveguide and the second input of the third optical hybrid circuit being coupled to a second end of the fourth waveguide, the third optical hybrid providing a plurality of mixing products.   
     
     
         9 . An optical device in accordance with  claim 8 , further including a plurality of photodiodes that receive the plurality of mixing products, the plurality of photodiodes supplying the outputs of the receiver to the control circuit. 
     
     
         10 . An optical device in accordance with  claim 9 , wherein the plurality of photodiodes are provided on the substrate. 
     
     
         11 . An optical device in accordance with  claim 1 , wherein each of the plurality of lasers is tunable. 
     
     
         12 . An optical device in accordance with  claim 1 , wherein each of the plurality of lasers is a local oscillator laser. 
     
     
         13 . An optical device in accordance with  claim 1 , further including:
 a first plurality of groups of photodiodes, each of which receiving outputs from a corresponding one of the plurality of first optical hybrid circuits; and   a second plurality of groups of photodiodes, each of which receiving outputs from a corresponding one of the plurality of second optical hybrid circuits.   
     
     
         14 . An optical device in accordance with  claim 13 , wherein the first plurality of groups of photodiodes and the second plurality of groups of photodiodes are provided on the substrate. 
     
     
         15 . An optical device in accordance with  claim 4 , wherein the substrate is a first substrate, the optical device further including:
 a second substrate having a third waveguide, the third waveguide supplying the second portion of the light from the second laser to the second control circuit.   
     
     
         16 . An optical device in accordance with  claim 1 , wherein the receiver is provided on the substrate. 
     
     
         17 . An optical device in accordance with  claim 1 , further including:
 a plurality of variable optical attenuators, each of which receiving the third portion of the light output from a corresponding one of the plurality of lasers, each of the plurality of variable optical attenuators being optically coupled to a respective one of a plurality of inputs of the multiplexer.   
     
     
         18 . An optical device in accordance with  claim 4 , wherein the first portion of the light supplied by the second laser is input to the receiver via the multiplexer. 
     
     
         19 . An optical device in accordance with  claim 4 , wherein second laser has first and second sides, the first portion of the light supplied by the second laser is output from the first side and the second portion of the light supplied by the second laser is output from the second side. 
     
     
         20 . An optical device in accordance with  claim 1 , wherein the plurality of lasers is a first plurality of lasers, the optical device further including:
 a second plurality of lasers provided on the substrate; and   a plurality of modulators provided on the substrate, each of which receiving an optical output from a corresponding one of the second plurality of lasers, each of the plurality of modulators supplying corresponding one of a plurality of modulated optical signals.   
     
     
         21 . An optical device in accordance with  claim 1 , wherein the plurality of lasers is a first plurality of lasers, and the substrate is a first substrate, the optical device further including:
 a second substrate;   a second plurality of lasers provided on the second substrate;   a plurality of modulators provided on the second substrate, each of which receiving an optical output from a corresponding one of the second plurality of lasers, each of the plurality of modulators supplying corresponding one of a plurality of modulated optical signals; and   an interposer substrate, the first and second substrates being provided on the interposer substrate.   
     
     
         22 . An optical device in accordance with  claim 1 , wherein the output of the multiplexer is a first output of the multiplexer, and the control circuit is a first control circuit, the multiplexer having a second output that is supplied to a second control circuit, the second control circuit being provided off the substrate. 
     
     
         23 . An optical device in accordance with  claim 1 , wherein the output of the multiplexer is a first output of the multiplexer, the substrate is a first substrate, and the control circuit is a first control circuit, the multiplexer having a second output that is supplied to a second control circuit, the second control circuit being provided on a second substrate. 
     
     
         24 . An optical device in accordance with  claim 1 , further including:
 a plurality of splitters provided on the substrate, each of which having first and second outputs, each said first output supplying said first portion of the light output from a respective one of the plurality of lasers, and each said second output supplying said second portion of the light output from said respective one of the plurality of lasers.