Panoramic reconstruction of temporal imaging

Patent metadata

Field	Value
Publication number	US-10429246-B2
Application number	US-201715792459-A
Country	US
Kind code	B2
Filing date	Oct 24, 2017
Priority date	Oct 24, 2017
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

The panoramic-reconstruction temporal imaging (PARTI) system is a single-shot optical waveform measurement apparatus that achieves scalable record length and sub-picosecond resolution simultaneously for ultrafast non-repetitive waveform characterization, in analogy with the wisdom of stitching multiple mosaic images to achieve larger-field-of-view in the spatial domain. It consists of a high-fidelity optical buffer, a low-aberration time magnifier and synchronization-control electronics. For specific measurement circumstances, the PARTI system can also be carried out based on a passive optical buffer, which reduces the system complexity. The PARTI system is configured for real-time single-shot characterization of non-repetitive optical dynamic waveform that evolves over a time scale much larger than that of its ultrafast temporal details, i.e., optical dynamics with large time-bandwidth product.

First claim

We claim:

1. A single-shot optical waveform measurement apparatus that achieves scalable record length and sub-picosecond resolution simultaneously for ultrafast non-repetitive waveform characterization comprises:
a fiber-loop based optical buffer that receives a signal under test, said buffer creating multiple identical replicas of the signal under test with a pre-defined period of T 1 ;
a time magnifier integrated with the buffer to realize temporal scanning using stroboscopic signal acquisition with a constant time interval, said magnifier measuring the replicas with a certain time period of T 2 ; and
clock and sync electronics that synchronize the buffer and magnifier such that if the measurement period of the time magnifier is T 2 , then in each frame, the time magnifier captures a different section of the long waveform of the signal under test with a step size equal to |T 1 -T 2 | in order to provide a magnified waveform corresponding to different sections of the signal under test.

2. The optical waveform measurement apparatus of claim 1 further including a real time recorder of the magnified waveform and a data processor that stitch together neighboring frames of the magnified waveform in order to reconstruct a magnified panoramic image of the original signal under test.

3. The optical waveform measurement apparatus of claim 2 wherein an effective single-shot recording length is scaled by the number of replicas without sacrificing the temporal resolution, thus substantially enhancing a time-bandwidth product (TBWP) of the apparatus.

4. The optical waveform measurement apparatus of claim 1 wherein the time magnifier comprises:
a first dispersion compensating fiber (DCF) and large effective area fiber (LEAF) combination for dispersing the signal from the optical buffer;
a mode-locked laser;
a second dispersion compensating fiber (DCF) and large effective area fiber (LEAF) combination for dispersing the output of the laser;
a wavelength-division multiplexer (WDM) that combines the output of the first DCF/LEAF combination and the pump (output of high power EDFA);
a highly-nonlinear fiber (HNLF) that receives the output of the WDM to generate an idler;
a first band-pass filter (BPF) that receives the idler output of the HNLF and limits it to a certain spectral component;
an output dispersion fiber (DCF) that passes the output of the first BPF;
a first low-noise Erbium-doped fiber amplifier (EDFA) that receives and amplifies the output of the DCF to form the output of the time magnifier.

5. The optical waveform measurement apparatus of claim 4 wherein the pump further includes:
a second low-noise Erbium-doped fiber amplifier (EDFA) for receiving the output of the second DCF/LEAF combination and pre-amplifying it;
a second band-pass filter (BPF) for filtering the output of the second EDFA;
a polarization controller (PC) for controlling the polarization of the output of the second BPF; and
a high-power Erbium-doped fiber amplifier (EDFA) that amplifies the output of the polarization controller to produce the pump.

6. The optical waveform measurement apparatus of claim 4 wherein the first dispersion compensating fiber (DCF) and large effective area fiber (LEAF) that form the combination are combined according to the ratio of their dispersion slope so as to provide linear net dispersion.

7. The optical waveform measurement apparatus of claim 5 wherein the second BPF selects the spectral component from 1555 nm to 1565 nm.

8. The optical waveform measurement apparatus of claim 1 wherein the fiber-loop optical buffer comprises:
an amplitude modulator (AM 1 ) for receiving a section of waveform of the signal under test;
a polarization controller for buffering the output of AM 1 ;
a 50/50 coupler for coupling the output of polarization controller into a fiber loop such that one replica of the signal under test is generated for each cavity round trip of the signal in the loop, said coupler further coupling out 50% of the buffered waveform as a replica of the signal in the loop to an output of the buffer, while the other 50% is circulated for the next round.

9. The optical waveform measurement apparatus of claim 8 wherein the fiber loop comprises:
an optical delay line after the coupler for fine tuning the cavity period of the loop to match a frame rate of the time magnifier;
a second amplitude modulator (AM 2 ) located after the delay line which functions as a switch by controlling the intra-cavity loss, said second amplitude modulator is turned on only when the signal in the loop passes it, such that it controls the number of replicas generated from the buffer;
a wavelength-division multiplexer (WDM) with a particular passband receives the signal from the second amplitude modulator and minimizes the buffering noise; and
an erbium-doped fiber (EDF) receives and amplifies the signal in the loop; and
a laser pumps the EDF so as to provide a maximum gain to compensate for the total cavity loss.

10. The optical waveform measurement apparatus of claim 9 wherein the fiber loop further includes a bandpass filter and polarization controller in series between the second amplitude modulator and the WDM.

11. The optical waveform measurement apparatus of claim 1 wherein the clock and sync electronics comprise:
a repetition-rate-stabilized femtosecond fiber (MLL);
a photodetector which with the MLL generates an electrical clock signal that serves as the time base of the whole system;
an arbitrary waveform generator (AWG),
a delay generator (DG) which with the AWG create electrical patterns that control the stroboscopic acquisition based on the clock signal; and
three amplitude modulators (AM 1 , AM 2 , AM 3 ) that convert the electrical patterns to the optical domain so as to control (a) the input signal under test loading (AM 1 ), optical-buffer switching (AM 2 ) and time-magnifier-pump generation (AM 3 ), respectively,
wherein after the signal under test is loaded into the buffer, AM 2 will be switched on only when the SUT arrives in each circulation to generate replicas; and
wherein AM 3 performs pulse-picking on the MLL to generate a pump for the time magnifier.

Assignees

• Univ Hong Kong

Inventors

• Wong Kenneth Kin Yip
• Li Bowen

Classifications

• H01S3/06791

  Fibre ring lasers (fibre laser gyrometers G01C19/72) · CPC title

• H01S3/06754

  Fibre amplifiers (H01S3/06708 takes precedence) · CPC title

• G02B6/2861

  using fibre optic delay lines and optical elements associated with them, e.g. for use in signal processing, e.g. filtering (delay lines in general H03H, H01P9/00; optical computing devices G06E) · CPC title

• H01S3/1003

  tunable optical elements, e.g. acousto-optic filters, tunable gratings · CPC title

• G01J11/00 Primary

  Measuring the characteristics of individual optical pulses or of optical pulse trains · CPC title