Optical-time-division-multiplexed transmission system using sinusoidally modulated optical signal as input pulse source

Patent metadata

Field	Value
Publication number	US-11799556-B2
Application number	US-202017631412-A
Country	US
Kind code	B2
Filing date	Feb 26, 2020
Priority date	Jul 30, 2019
Publication date	Oct 24, 2023
Grant date	Oct 24, 2023

Abstract

Disclosed are an optical-time-division-multiplexed transmission method and system using a simple sinusoidally modulated optical signal as an input pulse source. An optical-time-division-multiplexed transmission system comprises: an optical-time-division-multiplexed transmitter by applying a sinusoidal electrical signal, a first multi-level electrical PAM signal, and a second multi-level electrical PAM signal so as to generate an optical-time-division-multiplexed multi-level PAM signal; an optical detector for converting the transmitted optical-time-division-multiplexed PAM signal into an electrical signal; a time-division-demultiplexer for demultiplexing the detected electrical signal into two signals; a MIMO equalizer; and two decision elements for determining the levels of two demultiplexed signals obtained from the MIMO equalizer.

First claim

The invention claimed is:

1. An optical-time-division-multiplexed transmission system comprising:
an optical-time-division-multiplexed transmitter to generate an optical-time-division-multiplexed multi-level pulse-amplitude modulation (PAM) optical signal by applying a sinusoidal electrical signal, a first multi-level electrical PAM signal, and a second multi-level electrical PAM signal, wherein the optical-time-division-multiplexed transmitter comprises:
a first external modulator to modulate an optical output of a laser using a sinusoidal electrical signal to generate a sinusoidally modulated optical pulse,
an optical splitter to split the generated optical pulse into a first optical pulse and a second optical pulse,
a second external modulator to modulate the first optical pulse by applying the first multi-level electrical PAM signal,
a third external modulator to modulate the second optical pulse by applying the second multi-level electrical PAM signal,
a time delay to subject the first optical pulse, modulated by the second external modulator, to a time delay by half a pulse period so that the multiplexed optical pulses are orthogonal to each other in a time domain, and
an optical coupler to generate an optical-time-division-multiplexed signal by combining the time-delayed first optical pulse and the second optical pulse; and
an optical detector to convert the optical-time-division-multiplexed PAM signal transmitted through an optical fiber into an electrical signal.

2. The optical-time-division-multiplexed transmission system of claim 1 , wherein the optical-time-division-multiplexed transmitter further comprises:
a domain converter to convert the domain of the second optical pulse, modulated by the third external modulator, so that the multiplexed optical pulses also operate in mutually orthogonal domains including I/Q, different polarizations, or spatial modes,
wherein the optical coupler generates the optical-time-division-multiplexed signal by combining the time-delayed first optical pulse and the domain-converted second optical pulse.

3. The optical-time-division-multiplexed transmission system of claim 1 , wherein, to resolve the limitation of the extinction ratio of the sinusoidally modulated optical pulse that occurs by the bandwidth limitation of the external modulators, external modulators having a nonlinear transfer function are used, and a sinusoidal electrical signal with a predetermined amplitude or larger is applied so that the transfer function of the external modulators operate in the nonlinear region.

4. The optical-time-division-multiplexed transmission system of claim 3 , further comprising:
a time-division demultiplexer to demultiplex the electrical signal detected by the optical detector into two signals and to apply a multiple-input multiple-output (MIMO) equalizer to the signals; and
two decision elements to determine the levels of the two demultiplexed signals received from the MIMO equalizer.

5. The optical-time-division-multiplexed transmission system of claim 1 , further comprising:
a time-division demultiplexer to demultiplex the electrical signal detected by the optical detector into two signals and to apply a multiple-input multiple-output (MIMO) equalizer to the signals; and
two decision elements to determine the levels of two demultiplexed signals received from the MIMO equalizer.

6. An optical-time-division-multiplexed transmission system comprising:
an optical-time-division-multiplexed transmitter to generate an optical-time-division-multiplexed multi-level pulse-amplitude modulation (PAM) optical signal by applying a sinusoidal electrical signal, a first multi-level electrical PAM signal, and a second multi-level electrical PAM signal, wherein the optical-time-division-multiplexed transmitter comprises:
a directly modulated laser to generate a sinusoidally modulated optical pulse by applying a sinusoidal electrical signal to the laser;
an optical bandpass filter to pass only a wavelength component having a predetermined intensity or higher among the generated optical pulse to increase the extinction ratio of the optical pulse;
an optical splitter to split the optical pulse that has passed through the optical bandpass filter into a first optical pulse and a second optical pulse;
a first external modulator to modulate the first optical pulse by applying the first multi-level electrical PAM signal; and
a second external modulator to modulate the second optical pulse by applying the second multi-level electrical PAM signal.

7. The optical-time-division-multiplexed transmission system of claim 6 , wherein the optical-time-division-multiplexed transmitter further comprises:
a time delay to subject the first optical pulse, modulated by the first external modulator, to a time delay by half a pulse period so that the multiplexed optical pulses are orthogonal to each other in the time domain.

8. The optical-time-division multiplexed transmission system of claim 7 , further comprising:
a time-division demultiplexer to demultiplex the electrical signal detected by the optical detector into two signals and to apply a multiple-input multiple-output (MIMO) equalizer to the signals; and
two decision elements to determine the levels of two demultiplexed signals received from the MIMO equalizer.

9. The optical-time-division-multiplexed transmission system of claim 7 , wherein the optical-time-division-multiplexed transmitter further comprises:
a domain converter to convert a domain of the second optical pulse, modulated by the second external modulator, so that the multiplexed optical pulses also operate in mutually orthogonal domains including I/Q, different polarizations, or spatial modes; and
an optical coupler to generate an optical-time-division multiplexed optical signal by combining the time-delayed first optical pulse and the domain-converted second optical pulse.

10. An optical-time-division-multiplexed transmission method comprising:
generating an optical-time-division-multiplexed multi-level pulse-amplitude modulation (PAM) optical signal through an optical-time-division-multiplexed transmitter by applying a sinusoidal electrical signal, a first multi-level electrical PAM signal, and a second multi-level electrical PAM signal, wherein the generating comprises:
generating a sinusoidally modulated optical pulse by modulating an optical output of a laser with the sinusoidal electrical signal through a first external modulator,
splitting the generated optical pulse into a first optical pulse and a second optical pulse through an optical splitter,
modulating the first optical pulse through a second external modulator by applying the first multi-level electrical PAM signal; and modulating the second optical pulse through a third external modulator by applying the second multi-level electrical PAM signal,
subjecting the first optical pulse, modulated by the second external modulator, to a time delay by half a pulse period through a time delay so that the optical pulses are orthogonal to each other in a time domain, and
generating an optical-time-division-multiplexed signal through an optical coupler by combining the time-delayed first optical pulse and the second optical pulse; and
receiving the generated optical PAM signal and converting the received optical PAM signal into an electrical PAM signal through an optical detector.

11. The optical-time-division-multiplexed transmission method of claim 10 , wherein the generating of the optical-time-division-multiplexed multi-level PAM optical signal through the optical-time-division-multiplexed transmitter by applying the sinusoidal electrical signal, the first multi-level electrica

Assignees

• Korea Advanced Inst Sci & Tech

Inventors

• Chung Yun Chur
• Bae Sunghyun
• Kim Byunggon
• Kim Minsik

Classifications

• H04B10/524 Primary

  Pulse modulation · CPC title

• H04B10/2581

  Multimode transmission · CPC title

• H04B10/504 Primary

  using direct modulation · CPC title

• H04J14/08

  Time-division multiplex systems · CPC title

• H04L25/03891

  Spatial equalizers (MIMO diversity systems H04B7/0413) · CPC title