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. In addition, wavelength locker (WLL) circuitry may be provided on the PIC.

What is claimed is: 
     
         1 . An optical device, comprising:
 a first substrate;   a plurality of lasers provided on the first 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 first plurality of waveguides, each of which being optically coupled to a respective one of the first plurality of modulators, each of the first plurality of waveguides extending to an edge of the substrate and supplying a corresponding one of a first plurality of modulated optical signals;   a second plurality of optical waveguides, each of which being optically coupled to a corresponding one of the second plurality of modulators, each of the second plurality of waveguides extending to the edge of the substrate and supplying a corresponding one of a second plurality of modulated optical signals;   at least one rotator that rotates a polarization of the first plurality of modulated optical signals;   at least one polarization beam combiner configured to receive the polarization rotated first plurality of modulated optical signals and the second plurality of modulated optical signals, said at least one polarization beam combiner having at least one output that supplies the polarization rotated first plurality of modulated optical signals and the the second plurality of modulated optical signals, said at least one output of the polarization beam combiner being configured to be optically coupled to a plurality of optical fibers;   an integrated circuit, which provides radio frequency (RF) drive signals to the first plurality of modulators and the second plurality of modulators; and   a second substrate, the first substrate and the integrated circuit being provided on the second substrate.   
     
     
         2 . An optical device in accordance with  claim 1 , wherein the first substrate and the integrated circuit are flip chip and thermo-compression bonded to the second substrate. 
     
     
         3 . An optical device in accordance with  claim 1 , further including a heat spreader attached to the integrated circuit. 
     
     
         4 . An optical device in accordance with  claim 2 , wherein the optical device further comprises:
 a plurality of transmission lines that carries the radio frequency drive signals to the first plurality of modulators and the second plurality of modulators, wherein each of the first plurality of modulators constitutes a corresponding one of a first plurality of lumped elements and each of the second plurality of modulators constitutes a corresponding one of a second plurality of lumped elements.   
     
     
         5 . An optical device in accordance with  claim 4 , wherein the RF circuitry in the integrated circuit constitutes first circuitry, and the integrated circuit further including second circuitry that provides control signals to devices on the first substrate and receives monitoring signals indicative of a performance of the devices. 
     
     
         6 . An optical device in accordance with  claim 2 , wherein the integrated circuit includes RF circuitry, the second substrate further comprising:
 a plurality of transmission lines that carries the radio frequency drive signals from the RF circuitry to the first plurality of modulators and the second plurality of modulators, wherein each of the first plurality of modulators constitutes a corresponding one of a first plurality of traveling wave elements and each of the second plurality of modulators constitutes a corresponding one of a second plurality of traveling wave elements.   
     
     
         7 . An optical device in accordance with  claim 6 , wherein the circuitry constitutes first circuitry, the integrated circuit further including second circuitry that provides control signals to devices on the first substrate and receives monitoring signals indicative of a performance of the devices. 
     
     
         8 . An optical device in accordance with  claim 1 , further including:
 a plurality of lenses, each of which optically coupling a corresponding output of each of the plurality of polarization beam combiners to a corresponding one of a plurality of optical fibers.   
     
     
         9 . An optical device in accordance with  claim 1 , further including:
 a heat managing element that is thermally coupled to the first substrate, the heat managing element providing mechanical support to the first substrate, and the heat managing element transferring heat output from the first substrate, the heat managing element including at least one of a heat spreader, a thermal electric cooler, a heat pipe, and a heat sink.   
     
     
         10 . An optical device, comprising:
 a first substrate;   a plurality of lasers provided on the first substrate, each of the plurality of lasers being a local oscillator laser, each of the plurality of lasers being a local oscillator laser;   a first plurality of waveguides, each of which being provided on the first substrate and extending to an edge of the first substrate;   a second plurality of waveguides, each of which being provided on the first substrate and extending to the edge of the first substrate;   a first plurality of optical hybrid circuits provided on the first substrate, each of the first plurality of optical hybrid circuits receiving a respective one of a first plurality of optical signals from a corresponding one of the first plurality of waveguides and a first portion of light output from a respective one of the plurality of lasers, each of the first plurality of optical hybrid circuits providing a respective one of a first plurality of groups of mixing products; and   a second plurality of optical hybrid circuits provided on the first substrate, each of the second plurality of optical hybrid circuits receiving a respective one of a second plurality of optical signals from a corresponding one of the second plurality of waveguides and a second portion of the light output from a respective one of the plurality of lasers, each of the second plurality of optical hybrid circuits providing a respective one of a second plurality of groups of mixing products, the first and second pluralities of optical hybrid circuits being provided on the substrate;   first groups of photodiodes, each group of photodiodes of the first group of photodiodes receiving at least one output from a corresponding one of the first plurality of optical hybrid circuits;   second groups of photodiodes, each group of photodiodes of the second groups of photodiodes receiving at least one output from a corresponding one of the second plurality of optical hybrid circuits;   at least one polarization beam splitter to receive at at least one input a plurality of polarization multiplexed optical signals and supplying a first plurality of optical signals at at least a first output and a second plurality of optical signals at least a second output, said at least one polarization beam splitter being provided on the second substrate;   at least one polarization rotator that rotates a polarization of the first plurality of optical signals, such that the first plurality of optical signals is output from said at least one polarization rotator to a corresponding one of the plurality of third waveguides, and each of the second plurality of optical signals is output from said at least one polarization beam splitters to corresponding one of the plurality of fourth waveguides;   an integrated circuit, which receives radio frequency signals output from the first plurality of groups of photodiodes and the second plurality of groups of photodiodes; and   a second substrate, the first substrate and the integrated circuit being provided on the second substrate.   
     
     
         11 . An optical device in accordance with  claim 10 , wherein the first substrate and the integrated circuit are flip chip and thermo-compression bonded to the second substrate. 
     
     
         12 . An optical device in accordance with  claim 10 , further including a heat spreader attached to the integrated circuit. 
     
     
         13 . An optical device in accordance with  claim 11 , wherein the optical device further includes:
 a transmission line that carries the radio frequency signals, wherein each photodiode in each of the first groups of photodiodes and each photodiode in each of the second groups of photodiodes constitutes a lumped element.   
     
     
         14 . An optical device in accordance with  claim 13 , wherein the integrated circuit including first circuitry that receives the radio frequency signals and second circuitry that provides control signals to devices on the first substrate and receives monitoring signals indicative of a performance of the devices. 
     
     
         15 . An optical device in accordance with  claim 11 , wherein the optical device further comprising:
 a transmission line that carries the radio frequency signals, wherein each photodiode in each of the first groups of photodiodes and each photodiode in each of the second groups of photodiodes constitutes a traveling wave element.   
     
     
         16 . An optical device in accordance with  claim 15 , wherein the integrated circuit further including first circuitry that receives the radio frequency signals and second circuitry that provides control signals to devices on the first substrate and receives monitoring signals indicative of a performance of the devices. 
     
     
         17 . An optical device in accordance with  claim 10 , further including:
 a plurality of lenses, each of which optically coupling a corresponding output of each of the plurality of polarization beam combiners to a corresponding one of a plurality of optical fibers.   
     
     
         18 . An optical device in accordance with  claim 1 , wherein the first substrate and the integrated circuit are flip chip bonded to the second substrate. 
     
     
         19 . An optical device in accordance with  claim 10 , wherein the first substrate and the integrated circuit are flip chip bonded to the second substrate.