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 first plurality of modulators that respectively modulate a first optical output of each of the plurality of lasers, the first plurality of modulators being provided on the first substrate;   a second plurality of modulators that respectively modulate a second optical output of each of the plurality of lasers, the second plurality of modulators being provided on the first substrate;   a plurality of first waveguides, each of which being optically coupled to a respective one of the first plurality of modulators, 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 modulators;   a plurality of second optical waveguides, each of which being optically coupled to a corresponding one of the second plurality of modulators, each of the plurality of second waveguides extending to the edge of the substrate and being optically coupled to a respective one of the second plurality of modulators;   a plurality of taps provided on the substrate, each of the plurality of taps supplying a power split portion of each of a first plurality of optical signals, each of the first plurality of optical signals including first light from a respective one of the plurality of lasers; and   a plurality of variable optical attenuators provided on the substrate;   a receiver circuit, each of the plurality variable optical attenuator being configured to selectively supply at least a part of the power split portion of said each of the first plurality of optical signals to the receiver circuit; 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 , further comprising a third waveguide optically coupled to each of the plurality of variable optical attenuators, such that the third waveguide carries said at least part of the power split portion of each of the first plurality of optical signals selectively supplied to the receiver circuit. 
     
     
         3 . 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 a least a portion of which is provided to the third waveguide, such that the light is received by the receiver circuit. 
     
     
         4 . An optical device in accordance with  claim 3 , wherein the control circuit further adjusts the wavelength of each of the first plurality of optical signals based in part on a wavelength of the light output from the second laser. 
     
     
         5 . 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 provided to the third waveguide, such that the first portion of the light is received by the receiver circuit; and   a second control circuit that receives a second portion of the light, the second control circuit adjusting a wavelength of the light supplied by the second laser or- at least one of the plurality of lasers based on the second portion.   
     
     
         6 . An optical device in accordance with  claim 5 , wherein the second control circuit is provided off the substrate. 
     
     
         7 . An optical device in accordance with  claim 5 , wherein the second control circuit includes an etalon. 
     
     
         8 . An optical device in accordance with  claim 3 , wherein the second laser is a distributed feedback (DFB) laser. 
     
     
         9 . 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 and fourth waveguides, 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 power split portion of said each of the first plurality of optical signals, 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;   an optical hybrid circuit having first and second inputs, the first input of the optical hybrid circuit being coupled to a second end of the third waveguide and the second input of the optical hybrid circuit being coupled to a second end of the fourth waveguide, the optical hybrid providing a plurality of mixing products.   
     
     
         10 . An optical device in accordance with  claim 9 , 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. 
     
     
         11 . An optical device in accordance with  claim 10 , wherein the plurality of photodiodes are provided on the substrate. 
     
     
         12 . An optical device in accordance with  claim 1 , wherein the first plurality of optical signals is a first plurality of modulated optical signals, each of which being output from a respective one of the first plurality of modulators. 
     
     
         13 . An optical device in accordance with  claim 1 , wherein each of the first optical signals are input to a corresponding one of the first plurality of modulators. 
     
     
         14 . An optical device in accordance with  claim 1 , wherein each of the first plurality of modulators includes a nested modulator, the nested modulator including a first Mach-Zehnder modulator and a second Mach-Zehnder modulator, the first Mach-Zehnder modulator supplying an in-phase component of each of the first plurality of optical signals and the second Mach-Zehnder modulator supplying a quadrature component of each of the first plurality of optical signals. 
     
     
         15 . An optical device in accordance with  claim 1 , wherein each of the first plurality of modulators includes a first nested modulator, the first nested modulator including a first Mach-Zehnder modulator and a second Mach-Zehnder modulator, the first Mach-Zehnder modulator supplying a respective in-phase component of each of the first plurality of optical signals and the second Mach-Zehnder modulator supplying a respective quadrature component of each of the first plurality of optical signals, and
 each of the second plurality of modulators includes a second nested modulator, the second nested modulator including a first Mach-Zehnder modulator and a second Mach-Zehnder modulator, the first Mach-Zehnder modulator of each of the second nested modulators supplies a respective in-phase component of each of the second plurality of optical signals and a second Mach-Zehnder modulator of each of the second nested modulators supplies a respective quadrature component of each of the second plurality of optical signals.   
     
     
         16 . An optical device in accordance with  claim 1 , wherein each of the plurality of lasers is tunable. 
     
     
         17 . 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.   
     
     
         18 . An optical device in accordance with  claim 1 , wherein the first optical output of each of the plurality of lasers is supplied from a respective first side of each of the plurality of lasers, and second optical output of each of the plurality of lasers is supplied from a respective second side of each of the plurality of lasers. 
     
     
         19 . An optical device, comprising:
 a substrate;   a plurality of lasers provided on the substrate;   a plurality of splitters provided on the substrate, each of which receiving an optical output from a respective one of the plurality of lasers, each of the plurality of splitters having a first, second, and third output;   a first plurality of modulators that respectively modulate the first output of each of the plurality of splitters, the first plurality of modulators being provided on the first substrate;   a second plurality of modulators that respectively modulate the second output of each of the plurality of lasers, the second plurality of modulators being provided on the first substrate;   a plurality of first waveguides, each of which being optically coupled to a respective one of the first plurality of modulators, 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 modulators;   a plurality of second optical waveguides, each of which being optically coupled to a corresponding one of the second plurality of modulators, each of the plurality of second waveguides extending to the edge of the substrate and being optically coupled to a respective one of the second plurality of modulators;   a plurality of variable optical attenuators provided on the substrate, each of which receiving the third output of a respective one of the plurality of splitters;   a multiplexer that has a plurality of input coupled to a corresponding one of the plurality of variable optical attenuators, each of the variable optical attenuators selectively supplying at least a portion of the third output of a respective one of the plurality of splitters to a corresponding one of the plurality of inputs 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.   
     
     
         20 . An optical device in accordance with  claim 19 , 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 a least a portion of which is provided to the multiplexer, such that the light is received by the receiver circuit. 
     
     
         21 . An optical device in accordance with  claim 20 , 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. 
     
     
         22 . An optical device in accordance with  claim 19 , 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 provided to the receiver circuit; and   a second control circuit that receives a second portion of the light, the second control circuit adjusting a wavelength of the light supplied by the second laser based on the second portion.   
     
     
         23 . An optical device in accordance with  claim 22 , wherein the second control circuit is provided off the substrate. 
     
     
         24 . An optical device in accordance with  claim 22 , wherein the second control circuit includes an etalon. 
     
     
         25 . An optical device in accordance with  claim 20 , wherein the second laser is a distributed feedback (DFB) laser. 
     
     
         26 . An optical device in accordance with  claim 19 , wherein the plurality of splitters is a plurality of first splitters, 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 second splitter having an input that receives said at least a part of the power split portion of said each of the first plurality of optical signals, and first and second outputs, the first output of the second 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; and   an optical hybrid circuit having first and second inputs, the first input of the optical hybrid circuit being coupled to a second end of the third waveguide and the second input of the optical hybrid circuit being coupled to a second end of the fourth waveguide, the optical hybrid providing a plurality of mixing products, each of the plurality of mixing products including a portions of light supplied by the first input and the second input.   
     
     
         27 . An optical device in accordance with  claim 26 , 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. 
     
     
         28 . An optical device in accordance with  claim 27 , wherein the plurality of photodiodes are provided on the substrate. 
     
     
         29 . An optical device in accordance with  claim 19 , 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. 
     
     
         30 . An optical device in accordance with  claim 19 , 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.