# US 10,313,014 B2 · High capacity coherent optical transceiver for short reach applications > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,313,014 B2 - Document ID: US10313014B2 - Status: Granted - Kind: B2 - Application number: 15/718,417 - Filed: 2017-09-28 - Published: 2019-03-28 - Granted: 2019-06-04 - Earliest claimed: 2017-09-28 - Assignees: Ciena Corporation - Applicants: Ciena Corporation - Inventors: Michael Y. Frankel; Vladimir Pelekhaty - Web page: https://patentgrep.com/patent/US10313014B2 ## CPC - H04B 10/40: Transceivers - H04B 10/505: {using external modulation} - H04B 10/5053: {using a parallel, i.e. shunt, combination of modulators} - H04B 10/5162: {Return-to-zero modulation schemes} - H04B 10/532: Polarisation modulation - H04B 10/572: Wavelength control - H04B 10/588: in external modulation systems - H04B 10/61: Coherent receivers - 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 10/615: {Arrangements affecting the optical part of the receiver} - H04B 10/616: {Details of the electronic signal processing in coherent optical receivers} - H04B 10/6161: {Compensation of chromatic dispersion} - H04B 10/64: Heterodyne {, i.e. coherent receivers where, after the opto-electronic conversion, an electrical signal at an intermediate frequency [IF] is obtained} - G02F 1/212: {Mach-Zehnder type} - G02F 1/225: in an optical waveguide structure - H04B: TRANSMISSION - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS ## Abstract An optical transceiver includes a transmitter including transmitter signal processing circuitry configured to receive a transmit signal and provide two drive voltage signals V1, V2 to a modulator configured to modulate a laser based thereon; and a receiver including i) optical couplers configured to coherently combine received signals with a Local Oscillator (LO) formed by the laser and provide the combined signals to photodetectors for balanced detection, and ii) receiver signal processing circuitry configured to demodulate outputs from the balanced detection, wherein the receiver signal processing circuitry comprises an analog front-end and digital back-end. ## Claims ### Claim 1 An optical transceiver, comprising: a transmitter comprising transmitter signal processing circuitry configured to receive a transmit signal and provide two drive voltage signals V1, V2 to a modulator configured to modulate a laser based thereon; and a receiver comprising i) optical couplers configured to coherently combine received signals with a Local Oscillator (LO) formed by the laser and provide the combined signals to photodetectors for balanced detection, and ii) receiver signal processing circuitry configured to demodulate outputs from the balanced detection, wherein the receiver signal processing circuitry comprises an analog front-end and digital back-end, wherein the laser has a frequency offset based on signal bandwidth to provide a signal carrier for reuse as the LO. ### Claim 2 (depends on 1) The optical transceiver of claim 1, wherein the modulator comprises a Dual-Drive Mach-Zehnder Modulator (DD-MZM) with peak to peak drive voltages of the drive voltage signals V1, V2 sufficient to cover a full unity circle of an I/Q plane. ### Claim 3 (depends on 2) The optical transceiver of claim 2, wherein optical output field transitions across a predefined radial bisection line of the I/Q plane is prevented by providing the drive voltage signals V1, V2 to force null transmission, wherein the transmitter signal processing circuitry is configured to re-set the drive voltage signals V1, V2 for the null transmission. ### Claim 4 (depends on 3) The optical transceiver of claim 3, wherein the transmitter signal processing circuitry is configured to apply chromatic dispersion compensation on the transmit signal. ### Claim 5 (depends on 1) The optical transceiver of claim 1, wherein the transmitter signal processing circuitry is configured to add pilot tones to the transmitted signal, outside of signal spectrum and on opposite sides of the signal spectrum from an adjacent optical transceiver. ### Claim 6 (depends on 5) The optical transceiver of claim 5, wherein a first pilot tone of the pilot tones is at a fractional N/K of symbol clock outside of the signal spectrum, N and K are integers selected to place the pilot tones slightly outside of the signal spectrum, and a second pilot tone of the pilot tones, orthogonal to the first pilot tone, is at (N+1)/K of the symbol clock outside of the signal spectrum. ### Claim 7 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end comprises Transimpedance Amplifiers (TIAs) and analog Radio Frequency (RF) processing functions integrated into a same circuit. ### Claim 8 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end is configured to down-convert pilot tones on the received signals and directly synthesize a Radio Frequency (RF) LO signal for signal conversion to baseband with corresponding recovery of frequency and phase offsets. ### Claim 9 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end is configured to down-convert pilot tones on the received signals and directly synthesize a symbol clock signal. ### Claim 10 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end is configured to down-convert pilot tones on the received signals and directly synthesize a polarization deconvolution matrix. ### Claim 11 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end is configured to down-convert the received signals to baseband and extract I and Q components. ### Claim 12 (depends on 1) The optical transceiver of claim 1, wherein the analog front-end comprises Finite Impulse Response (FIR) filters for partial compensation of chromatic dispersion compensation, in combination with the transmitter signal processing circuitry of an adjacent optical transceiver. ### Claim 13 (depends on 12) The optical transceiver of claim 12, wherein unused FIR filter taps in the analog front-end are shut down to conserve power. ### Claim 14 (depends on 1) The optical transceiver of claim 1, wherein an Analog to Digital Converter (ADC) stage is between the analog front-end and the digital back-end, wherein the ADC stage operates at a symbol rate. ### Claim 15 (depends on 14) The optical transceiver of claim 14, wherein an Effective Number of Bits (ENOB) of the ADC stages is limited to provide hard decision slicing of a symbol constellation. ### Claim 16 (depends on 1) The optical transceiver of claim 1, wherein the digital back-end comprises a Digital Signal Processor (DSP) configured to perform signal decoding and Forward Error Correction (FEC) decoding. ### Claim 17 (depends on 1) The optical transceiver of claim 1, wherein the transmitter and the receiver are housed in a housing compliant to one of Quad Small Form-factor Pluggable (QSFP) Double Density (DD) and Octal Small Form-factor Pluggable (OSFP). ### Claim 18 An optical transceiver, comprising: a transmitter comprising transmitter signal processing circuitry configured to receive a transmit signal and provide two drive voltage signals V1, V2 to a modulator configured to modulate a laser based thereon, wherein the transmitter signal processing circuitry is configured to add pilot tones to the transmitted signal, outside of signal spectrum and on opposite sides of the signal spectrum from an adjacent optical transceiver; and a receiver comprising i) optical couplers configured to coherently combine received signals with a Local Oscillator (LO) formed by the laser and provide the combined signals to photodetectors for balanced detection, and ii) receiver signal processing circuitry configured to demodulate outputs from the balanced detection, wherein the receiver signal processing circuitry comprises an analog front-end and digital back-end. ### Claim 19 (depends on 18) The optical transceiver of claim 18, wherein a first pilot tone of the pilot tones is at a fractional N/K of symbol clock outside of the signal spectrum, N and K are integers selected to place the pilot tones slightly outside of the signal spectrum, and a second pilot tone of the pilot tones, orthogonal to the first pilot tone, is at (N+1)/K of the symbol clock outside of the signal spectrum. ### Claim 20 An optical transceiver, comprising: a transmitter comprising transmitter signal processing circuitry configured to receive a transmit signal and provide two drive voltage signals V1, V2 to a modulator configured to modulate a laser based thereon; and a receiver comprising i) optical couplers configured to coherently combine received signals with a Local Oscillator (LO) formed by the laser and provide the combined signals to photodetectors for balanced detection, and ii) receiver signal processing circuitry configured to demodulate outputs from the balanced detection, wherein the receiver signal processing circuitry comprises an analog front-end and digital back-end, wherein the analog front-end comprises Finite Impulse Response (FIR) filters for partial compensation of chromatic dispersion compensation, in combination with the transmitter signal processing circuitry of an adjacent optical transceiver.