# US 9,882,652 B2 · Methods and systems for optical detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,882,652 B2 - Document ID: US9882652B2 - Status: Granted - Kind: B2 - Application number: 14/698,562 - Filed: 2015-04-28 - Published: 2016-11-03 - Granted: 2018-01-30 - Earliest claimed: 2015-04-28 - Assignees: LGS Innovations LLC - Applicants: Lgs Innovations LLC - Inventors: Thomas H. Wood - Web page: https://patentgrep.com/patent/US9882652B2 ## 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 10/11: Arrangements specific to free-space transmission, i.e. transmission through air or vacuum - H04B 10/524: Pulse modulation - H04B 10/532: Polarisation modulation - H04B 10/612: {for optical signals modulated with a format different from binary or higher-order PSK [X-PSK], e.g. QAM, DPSK, FSK, MSK, ASK} - H04B 10/616: {Details of the electronic signal processing in coherent optical receivers} - H04B: TRANSMISSION ## Abstract The present application is directed an optical communication method. The method includes a step of receiving a signal at a single-polarization receiver. The method also includes a step of detecting, through the single-polarization receiver, the signal including a symbol with a pulse position modulation pulse and an additional modulation. The method also includes a step of decoding a first portion of bits carried by the symbol based on a position of the PPM pulse. Further, the method includes a step of decoding a second portion of the bits at the position through an additional modulation. The application is also directed to an apparatus for optical communication. In addition, the application is directed to an optical communication method which recovers two polarization components form the signal each carrying independent data. Further, the application is directed to an optical communication method that recovers two frequencies of the detected signal. ## Claims ### Claim 1 An optical communication method comprising: receiving a signal at a single-polarization receiver; detecting, through the single-polarization receiver, the signal including a symbol with a pulse position modulation (PPM) pulse and an additional modulation; decoding a first nonzero portion of bits carried by the symbol based on a position of the PPM pulse; and decoding a second nonzero portion of the bits at the position through an additional modulation. ### Claim 2 (depends on 1) The method of claim 1, wherein the first portion of bits includes log2(M) bits, and the second portion of bits includes 4 bits. ### Claim 3 (depends on 1) The method of claim 1, wherein the position includes a slot ‘m’ in a timeframe ranging from 2 to 32. ### Claim 4 (depends on 3) The method of claim 3, wherein the step of decoding the first portion of bits includes determining a first set of slots of plural slot positions for the symbol, the first set having the greatest energy for the symbol, and correlating the first set to a corresponding bit pattern. ### Claim 5 (depends on 1) The method of claim 1, wherein the additional modulation is selected from phase-shift keying (PSK) modulation, Quadrature Phase Shift Keying (QPSK), quadrature-amplitude modulation (QAM) and combinations thereof. ### Claim 6 (depends on 1) The method of claim 1, wherein the receiver is a coherent receiver. ### Claim 7 (depends on 1) The method of claim 1, wherein the symbol includes plural PPM pulses having additional modulation in plural, corresponding positions. ### Claim 8 (depends on 1) The method of claim 1, wherein the signal exhibits a theoretical receiver sensitivity less than 6.5 dB at a Bit Error Rate greater than 10−3. ### Claim 9 (depends on 1) The method of claim 1, wherein the signal exhibits a data rate reduction less than about 50% of that exhibited for a PQP Classic modulation format. ### Claim 10 (depends on 9) The method of claim 9, wherein the signal exhibits a data rate reduction less than about 40% of that exhibited for PQP Classic modulation format. ### Claim 11 (depends on 1) The method of claim 1, wherein the signal exhibits a theoretical receiver sensitivity less than a 1 dB photons per bit difference, when measured at a BER of 10−3, in relation to a PQP Classic coherent receiver. ### Claim 12 An apparatus comprising: a single-polarization receiver front end that detects a signal including a symbol having a pulse position modulation (PPM) pulse; an analog-to-digital convertor (ADC) that converts the detected signal into a digital component; and a processor, operably coupled to the single-polarization receiver and the ADC, the processor configured to decode a first non-zero portion of a plurality of bits carried by the symbol based on a position of the PPM pulse. ### Claim 13 (depends on 12) The apparatus of claim 12, further comprising: a polarization maintaining (PM) component operably coupled to the ADC. ### Claim 14 An optical communication method, comprising: receiving a signal at a receiver; detecting, through the receiver, a signal including a symbol with an independent pulse position modulation (PPM) pulse and an additional modulation; recovering two polarization components from the detected signal, each of the polarization components carrying independent data in different timeslots; decoding a first portion of bits carried by the symbol based on a position of the PPM pulse; and decoding a second portion of the bits based on the additional modulation. ### Claim 15 (depends on 14) The method of claim 14, wherein the signal exhibits a receiver sensitivity, measured at a bit error rate of 10−3, within 10% of a receiver sensitivity of a signal having polarization components carrying dependent data. ### Claim 16 (depends on 14) The method of claim 14, wherein the signal exhibits a capacity more than about 10% of a signal for a PQP Classic receiver operating with the same speed analog to digital converter. ### Claim 17 An optical communication method, comprising: receiving a signal at a coherent receiver; detecting, through the coherent receiver, the signal including a symbol with a pulse position modulation (PPM) pulse; recovering a first and a second frequency of the detected signal; and decoding a first non-zero portion of bits carried by the symbol based on a position of the PPM pulse. ### Claim 18 (depends on 17) The method of claim 17, further comprising: decoding a second non-zero portion of a plurality of bits carried by the symbol based on an additional modulation in the first frequency. ### Claim 19 (depends on 17) The method of claim 17, wherein the position includes a timeslot in a frame, and the symbol in the timeslot of the first frequency is rotated by another timeslot with respect to a second symbol in the second frequency. ### Claim 20 (depends on 19) The method of claim 19, wherein the signal exhibits a receiver sensitivity less than about 5.7 dB, at 2 timeslots in a frame and a Bit Error Rate greater than 10−3.