Diagnostic waveguide for optical chip testing

Abstract

A photonics system includes a transmit photonics module and a receive photonics module. The photonics system also includes a transmit waveguide coupled to the transmit photonics module, a first optical switch integrated with the transmit waveguide, and a diagnostics waveguide optically coupled to the first optical switch. The photonics system further includes a receive waveguide coupled to the receive photonics module and a second optical switch integrated with the receive waveguide and optically coupled to the diagnostics waveguide.

1 . (canceled) 
     
     
         2 . A photonics system comprising:
 a transmitter;   a receiver;   a transmit waveguide coupled to the transmitter;   a receive waveguide coupled to the receiver;   a first variable coupler integrated with the transmit waveguide;   a second variable coupler integrated with the receive waveguide; and   a diagnostics waveguide optically coupled with the first variable coupler and the second variable coupler.   
     
     
         3 . The photonics system of  claim 2 , wherein the first variable coupler is configurable to variably couple up to all of the light from the transmit waveguide into the diagnostics waveguide. 
     
     
         4 . The photonics system of  claim 2 , wherein:
 the first variable coupler is a Mach-Zehnder interferometer comprising an input, a first arm, a second arm, a first output, and a second output;   the input is coupled with the transmitter by the transmit waveguide;   the first output is coupled to a terminal portion of the transmit waveguide; and   the second output is coupled to the diagnostics waveguide.   
     
     
         5 . The photonics system of  claim 4 , wherein the first arm and the second arm of the Mach-Zehnder interferometer are optical waveguides. 
     
     
         6 . The photonics system of  claim 5 , further comprising a heater, wherein:
 a voltage applied to the heater is configured to control a phase of light in the first arm of the Mach-Zehnder interferometer; and   the phase of light in the first arm compared to a phase of light in the second arm is used to control coupling from the input to the first output and to the second output.   
     
     
         7 . The photonics system of  claim 5 , further comprising a diode-based phase control element, wherein:
 a voltage applied to the diode-based phase control element is configured to control a phase of light in the first arm of the Mach-Zehnder interferometer; and   the phase of light in the first arm compared to a phase of light in the second arm is used to control coupling from the input to the first output and to the second output.   
     
     
         8 . The photonics system of  claim 2 , wherein the first variable coupler is a ring resonator interferometer comprising an input, a waveguide ring, a first output, and a second output. 
     
     
         9 . The photonics system of  claim 8 , further comprising a heater, wherein a voltage applied to the heater is configured to control an optical resonance wavelength of the waveguide ring to control optical coupling from the input to the first output and to the second output. 
     
     
         10 . The photonics system of  claim 8 , further comprising a diode-based phase control element, wherein a voltage applied to the diode-based phase control element is configured to control an optical resonance wavelength of the waveguide ring to control optical coupling from the input to the first output and to the second output. 
     
     
         11 . The photonics system of  claim 2 , wherein the transmitter, the receiver, the trasmit waveguide, the receive waveguide, the first variable coupler, and the second variable coupler are integreated on a chip. 
     
     
         12 . The photonics system of  claim 11 , wherein the chip is part of an undiced wafer. 
     
     
         13 . The photonics system of  claim 2 , wherein the first variable coupler is configured to be thermally actuated. 
     
     
         14 . The photonics system of  claim 2 , wherein the first variable coupler is configured to be electrically actuated. 
     
     
         15 . A method of performing testing of a photonic device, the method comprising:
 providing a photonics system having:
 a transmitter; 
 a receiver; 
 a transmit waveguide coupled to the transmitter; 
 a receive waveguide coupled to the receiver; 
 a first variable coupler integrated with the transmit waveguide; 
 a second variable coupler integrated with the receive waveguide; and 
 a diagnostics waveguide optically coupled with the first variable coupler and the second variable coupler; 
   generating a test pattern;   generating, with the transmitter, an optical signal associated with the test pattern;   transmitting the optical signal through the transmit waveguide;   coupling at least a portion of the optical signal into the diagnostics waveguide to provide a diagnostics signal;   coupling at least a portion of the diagnostics signal into the receive waveguide; and   testing the diagnostics signal.   
     
     
         16 . The method of  claim 15  wherein the transmitter, the transmit waveguide, and the diagnostics waveguide are integrated on a chip. 
     
     
         17 . The method of  claim 15 , further comprising applying a voltage to the first variable coupler to change an amount of light coupled from the transmit waveguide into the diagnostics waveguide. 
     
     
         18 . The method of  claim 17 , wherein the voltage is a first voltage, and the method further comprises applying a second voltage to the first variable coupler, concurrently with applying the first voltage, to change an amount of light coupled from the transmit waveguide into the diagnostics waveguide. 
     
     
         19 . The method of  claim 17 , further comprising applying a voltage to the second variable coupler to change an amount of light coupled from the diagnostics waveguide into the receive waveguide. 
     
     
         20 . The method of  claim 15 , wherein the first variable coupler comprises a ring waveguide. 
     
     
         21 . A photonics system comprising:
 a transmitter;   a receiver;   a transmit waveguide coupled to the transmitter;   a receive waveguide coupled to the receiver;   a first variable coupler integrated with the transmit waveguide, wherein the first variable coupler is configured to be thermally actuated;   a second variable coupler integrated with the receive waveguide, wherein the second variable coupler is configured to be thermally actuated; and   a diagnostics waveguide optically coupled with the first variable coupler and the second variable coupler, wherein the transmitter, the receiver, the transmit waveguide, the receive waveguide, the first variable coupler, the second variable coupler, and the diagnostics waveguide are integrated on a chip.