# US 11,112,306 B2 · Real-time optical spectro-temporal analyzer and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,112,306 B2 - Document ID: US11112306B2 - Status: Granted - Kind: B2 - Application number: 16/496,748 - Filed: 2017-03-23 - Published: 2020-01-30 - Granted: 2021-09-07 - Earliest claimed: 2017-03-23 - Assignees: The University of Hong Kong - Applicants: The University of Hong Kong - Inventors: Kin Yip Kenneth Wong; Xiaoming Wei; Bowen Li; Ying Yu; Chi Zhang - Web page: https://patentgrep.com/patent/US11112306B2 ## CPC - G01J 1/00: Photometry, e.g. photographic exposure meter (spectrophotometry G01J3/00; specially adapted for radiation pyrometry G01J5/00 {; exposure meters built in cameras G03B17/06}) - G01J 3/1895: {using fiber Bragg gratings or gratings integrated in a waveguide} - G01J 3/0218: {using optical fibers} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) ## Abstract An optical signal analyzing apparatus enables real-time and single-shot analysis simultaneously in both time and frequency domains with spectro-temporal analysis. The apparatus includes a fiber tap coupler for receiving an input optical signal from continuous wave (CW) to ultra-short pulses (femtosecond-picosecond). An optical splitter directs part of the signal to a frequency channel and part to a time channel A photodiode in the time channel directly monitors the intensity evolution and converts it to an electrical signal. In the frequency channel, two sub-channels are provided: one for CW/quasi-CW and one for short-pulse components. A signal processor analyses the time- and frequency-domain data from the time channel and frequency channel and displays the temporal and spectral evolutions simultaneously, so that the two different pieces of information of a non-repeated dynamic event can be correlated in different domains. ## Claims ### Claim 1 A versatile optical signal analyzing apparatus that enables real-time and single-shot analysis in both time and frequency domains simultaneously for non-repetitive ultrafast optical events with spectro-temporal analysis, comprises: a fiber-tap coupler for receiving an input optical signal from continuous wave (CW) to ultra-short pulses; an optical splitter which directs part of the input optical signal to a frequency channel and part to a time channel; a high-speed photodiode in the time channel directly monitors time domain intensity evolution and converts it to an electrical signal; two sub-channels specified for CW/quasi-CW and short-pulse components form the frequency channel in which spectroscopes determine frequency domain spectral intensity evolution for the CW/quasi-CW and short-pulse components, respectively; a signal processor that analyses the frequency and time domain intensity evolutions from the time channel and frequency channels; and a display of the time domain intensity evolution and frequency domain spectral intensity evolutions simultaneously so that the frequency and time domain evolutions of a non-repeated dynamic event can be correlated in the frequency and time domains. ### Claim 2 (depends on 1) The optical signal analyzing apparatus of claim 1 wherein the input optical signal can be from any optical sources at wavelengths within the operating window of a real time optical spectra-temporal analyzer (ROSTA), i.e., 1400-1700 nm for short pulse component and 1538-1543 nm for CW/quasi-CW component. ### Claim 3 (depends on 1) The optical signal analyzing apparatus of claim 1 wherein the photodiode has a bandwidth of at least 10 GHz, and a temporal resolution is 10's of ps for time-domain information. ### Claim 4 (depends on 1) The optical signal analyzing apparatus of claim 1 wherein the time channel further includes a multi-channels digitizer that samples the electrical signal from the photodiode at a Nyquist rate and with a time record in the millisecond range. ### Claim 5 (depends on 4) The optical signal analyzing apparatus of claim 4 wherein the data rate of the electrical signal from the multi-channels digitizer is 40 GS/s and its temporal resolution is ˜50 ps. ### Claim 6 (depends on 1) The optical signal analyzing apparatus of claim 1 wherein the sub-channels in the frequency channel are complementary and respectively visualize the ultra-short-pulse components with a pulse/time stretch (TS) spectroscope and the CW/quasi-CW components with a CW/time lens (TL) spectroscope in a single-shot manner. ### Claim 7 (depends on 6) The optical signal analyzing apparatus of claim 6 wherein in the pulse/TS spectroscope, the optical signal is linearly chirped by a large group-velocity dispersion (GVD) medium so that different wavelength components propagate at different group velocities, thus performing frequency-to-time mapping for ultra-short-pulses. ### Claim 8 (depends on 7) The optical signal analyzing apparatus of claim 7 wherein the spectral information in the pulse/TS spectroscope is also detected by a high-speed photo detector. ### Claim 9 (depends on 7) The optical signal analyzing apparatus of claim 7 wherein a spectral resolution of the pulse/TS spectroscope is largely determined by the dispersion amount of the GVD medium, where the dispersive media is one of a dispersive fiber and chirped fiber Bragg grating (CFBG). ### Claim 10 (depends on 6) The optical signal analyzing apparatus of claim 6 wherein the CW/TL spectroscope is a temporal imaging system enabling ultrafast spectral analysis through temporal focusing by incorporating one of temporal quadratic phase modulation and dispersion, and temporal imaging. ### Claim 11 (depends on 10) The optical signal analyzing apparatus of claim 10 wherein the CW/TL spectroscope focuses different optical frequency components into short pulses with different time delays, thus realizing a frequency-to-time mapping for CW/quasi-CW components. ### Claim 12 (depends on 6) The optical signal analyzing apparatus of claim 6 wherein the CW/TL spectroscope comprises a quadratic phase modulation device that receives an input CW/quasi-CW signal and performs four-wave mixing (FWM1) of the input signal, the output of the quadratic phase modulation device is applied to a Phase Conjugation device that performs a second four-wave mixing (FWM2), and the output of the Phase Conjugation device is applied to a GVD medium to form the transform-limited output. ### Claim 13 (depends on 12) The optical signal analyzing apparatus of claim 12 wherein the Quadratic Phase modulation device comprises a wavelength-division multiplexing (WDM) circuit that mixes the input signal with a signal from a swept pump, the WDM circuit output is passed through a highly nonlinear dispersion-shifted fiber HNL-DSF1 to an optical coupler (OC) to form the output of the Quadratic Phase modulation device. ### Claim 14 (depends on 13) The optical signal analyzing apparatus of claim 13 wherein the swept pump comprises a mode-locked laser (MLL) whose output is applied to a GVD medium, the GVD output is received by an erbium-doped fiber amplifier (EDFA), the amplifier output is passed through a band-pass filter (BPF) to a second EDFA and then to a polarization controller (PC) which outputs the swept frequency signal. ### Claim 15 (depends on 12) The optical signal analyzing apparatus of claim 12 wherein the Phase Conjugation device comprises an OC that couples the input signal with a CW pump signal, the output of the OC is passed through a highly nonlinear dispersion-shifted fiber HNL-DSF2 and a filter to form the output of the Phase Conjugation device. ### Claim 16 (depends on 15) The optical signal analyzing apparatus of claim 15 wherein the CW pump signal of FWM2 is generated by a CW Source whose output is passed through an isolator (ISO), the ISO signal is received by an EDFA, which passes it to a PC to form the CW pump signal. ### Claim 17 (depends on 1) The optical signal analyzing apparatus of claim 1 wherein the signal processor preforms channel alignment of the signals in the time channel and the signal in the sub-channels in the frequency domain, calibrates the wavelength and intensity of the channel signals and combines the aligned and calibrated channel signals. ### Claim 18 A method for signal analysis of non-recurring optical phenomenon ranging from ultra-short pulses (femtosecond to picosecond) to quasi-CW in real-time in both time and frequency domains simultaneously for non-repetitive ultrafast optical events with spectral analysis, comprising the steps of: receiving an input optical signal in the range from ultra-short pulses to CW; directing part of the input optical signal to a frequency channel and part to a time channel; directly monitoring with a photodiode in the time channel an intensity evolution of the input optical signal and converting it to an electrical signal; directing the input optical signal in the frequency channel into two sub-channels specified for CW/quasi-CW and short-pulse components, respectively, one sub channel processes the signal by a time stretch (TS) process and the other processes the signal by a parametric time-lens (TL) imaging process to form a frequency domain spectral intensity evolution; analyzing in a processor the time- and frequency-domain intensity evolutions respectively from the time channel and frequency channel; and displaying the analyzed time domain and frequency domain intensity spectral evolutions simultaneously so that the frequency and time domain evolutions of a non-recurring dynamic event can be correlated in the frequency and time domains. ### Claim 19 (depends on 18) The method of claim 18 wherein the TL imaging process of one of the sub-channels of the frequency channel involves the steps of: applying the input signal to a quadratic phase modulation device; mixing the input signal in a WDM circuit of the quadratic-phase modulation device with a signal from a swept pump; passing the output from a highly nonlinear dispersion-shifted fiber (HNL-DSF1) to an optical coupler; forming the output of the optical coupler as the output of quadratic phase modulation device; applying the output of the quadratic phase modulation device to a phase conjugation device, coupling quadratic phase modulation device output with a CW pump signal through an optical coupler of the phase conjugation device, passing the coupled signal through a second highly nonlinear dispersion-shifted fiber (HNL-DSF2); filtering the output of the HNL-DSF2; and passing the filter output through a large GVD medium to form the TLS signal.