# US 2013/0156424 A1 · Apparatus for measuring performance of coherent optical receiver > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0156424 A1 - Document ID: US20130156424A1 - Status: Published application - Kind: A1 - Application number: 13/687,741 - Filed: 2012-11-28 - Published: 2013-06-20 - Earliest claimed: 2011-12-14 - Assignees: Electronics and Telecommunications Research Institute - Inventors: Chun Ju YOUN; Joong-Seon Choe; Jong-Hoi Kim; Duk Jun Kim; Yong-Hwan Kwon; Eun Soo Nam - Web page: https://patentgrep.com/patent/US20130156424A1 ## CPC - H04B 10/614: {comprising one or more polarization beam splitters, e.g. polarization multiplexed [PolMux] X-PSK coherent receivers, polarization diversity heterodyne coherent receivers (H04J14/06 takes precedence)} - H04B 10/0799: {Monitoring line transmitter or line receiver equipment} - H04B: TRANSMISSION ## Abstract An apparatus for measuring performance of a coherent optical receiver includes a beam splitter splitting light into first and second paths, a first optical modulator modulating the first path light, a variable optical attenuator controlling an optical power of the first optical modulator, a first polarization controller transmitting a signal controlling polarization of an output of the variable optical attenuator to the coherent optical receiver, a second optical modulator modulating the second path light, a variable optical delay line delaying time of an output of the second optical modulator, a second polarization controller transmitting a signal controlling polarization of an output of the variable optical delay line to the coherent optical receiver, a network analyzer measuring performance of the coherent optical receiver and controlling the optical modulators, and a controller transmitting a control signal to the optical modulators. ## Claims ### Claim 1 An apparatus for measuring performance of a coherent optical receiver, comprising: a beam splitter configured to split light received from a light source into a first path light and a second path light; a first optical modulator configured to receive the first path light of the beam splitter and optically modulate the received first path light; a variable optical attenuator configured to control and output an optical power of an output of the first optical modulator; a first polarization controller configured to transmit a first output signal controlling polarization of an output of the variable optical attenuator to the coherent optical receiver; a second optical modulator configured to receive the second path light of the beam splitter and optically modulate the received second path light; a variable optical delay line configured to delay and output time of an output of the second optical modulator; a second polarization controller configured to transmit a second output signal controlling polarization of an output of the variable optical delay line to the coherent optical receiver; a network analyzer configured to receive an output of the coherent optical receiver to measure performance of the coherent optical receiver and control the first optical modulator and the second optical modulator; and a controller configured to receive a control signal from the network analyzer and transmit the received control signal to the first optical modulator and the second optical modulator. ### Claim 2 (depends on 1) The apparatus as set forth in claim 1, wherein the variable optical attenuator controls the optical power of the output of the first optical modulator such that the first output signal and the second output signal transmitted to the coherent optical receiver have the same optical power. ### Claim 3 (depends on 1) The apparatus as set forth in claim 1, wherein the first polarization controller controls the polarization of the output of the variable optical attenuator such that the first output signal and the second output signal transmitted to the coherent optical receiver have the same polarization. ### Claim 4 (depends on 1) The apparatus as set forth in claim 1, wherein the second polarization controller controls the polarization of the output of the variable optical attenuator such that the first output signal and the second output signal transmitted to the coherent optical receiver have the same polarization. ### Claim 5 (depends on 1) The apparatus as set forth in claim 1, wherein the variable optical delay line controls time of the output of the second optical modulator such that the first output signal and the second output signal transmitted to the coherent optical receiver are made identical in time synchronization. ### Claim 6 (depends on 1) The apparatus as set forth in claim 1, wherein the network analyzer receives an output of the coherent optical receiver to measure bandwidth, common mode rejection ratio or channel skew of the coherent optical receiver. ### Claim 7 (depends on 1) The apparatus as set forth in claim 1, wherein the first optical modulator and the second optical modulator optically modulate the first path light and the second path light of the beam splitter, respectively such that the first output signal and the second output signal transmitted to the coherent optical receiver have same phase and intensity. ### Claim 8 (depends on 1) The apparatus as set forth in claim 1, wherein the first optical modulator and the second optical modulator optically modulate the first path light and the second path light of the beam splitter, respectively such that the first output signal and the second output signal transmitted to the coherent optical receiver have same intensity and opposite phases. ### Claim 9 (depends on 1) The apparatus as set forth in claim 1, wherein the controller controls the first optical modulator and the second optical modulator such that the first output signal and the second output signal transmitted to the coherent optical receiver have same phase and intensity. ### Claim 10 (depends on 9) The apparatus as set forth in claim 9, wherein the controller is a power divider. ### Claim 11 (depends on 1) The apparatus as set forth in claim 1, wherein the controller controls the first path light and the second path light of the beam splitter such that the first output signal and the second output signal transmitted to the coherent optical receiver have same intensity and opposite phases. ### Claim 12 (depends on 11) The apparatus as set forth in claim 11, wherein the controller is a 180-degree hybrid.