Time sampled photodetector devices and methods

Patent metadata

Field	Value
Publication number	US-9917650-B2
Application number	US-201615248582-A
Country	US
Kind code	B2
Filing date	Aug 26, 2016
Priority date	Sep 25, 2015
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

Photonic integration has primarily sought to exploit optical parallelism through wavelength division multiplexing whilst in many instances “brute-force” time division multiplexing offers benefits through reduced complexity and cost. However, photoreceivers are primarily the same now for operation at 10 Gb/s, 20 Gb/s, 40 Gb/s and above as 20 or 25 years ago and exploit the same optical detection—amplification—logic processing design. However, high speed low cost electronics ca be leveraged in conjunction with optical time sampling and logic to provide a new design paradigm. An incoming XGbs −1 optical data stream is sampled and processed by N photodetectors each operating at (X/N)Gbs −1 rather than the current direct XGbs −1 front-end of the prior art. Flexibility for the designer in establishing N within optical layer constraints, electronics capabilities etc. allows for further cost—power—complexity—performance tradeoffs to be established in different systems such that high capacity TDM links can exploit direct CMOS integrated optoelectronic front-ends.

First claim

What is claimed is:

1. A method comprising:
receiving an optical input amplitude modulated at a predetermined data rate X Gb/s;
optically splitting the received optical signal into N optical channels at X Gb/s and coupling each channel to a predetermined optical detector, wherein the optical signal at each optical detector differs in time relative to the optical signal at an adjacent optical detector by that equivalent to a single bit at X Gb/s;
time averaging the output of each optical detector for a duration equivalent to N bits at X Gb/s;
gating the time averaged signal from each optical detector at a rate of X/N Gb/s to generate N streams of symbols; and
digitally processing the N streams of symbols to generate the original X Gb/s data.

2. The method according to claim 1 , wherein
time averaging the output of an optical detector comprises employing a resistive—capacitive network between the output of the optical detector and a transimpedance amplifier for converting a time averaged photocurrent to voltage; and
gating the time averaged photocurrent comprises activating a switch disposed between the resistive—capacitive network and the transimpedance amplifier.

3. The method according to claim 1 , wherein
digitally processing the N streams of symbols comprises:
initializing the processing with a first set of gated time averaged data;
establishing a first iteration with the next gated time average data and deducing an original unknown N bits from the N symbols and their equations defining each time averaged data set to a block of received N bits;
continuing to iterate using the currently known input bits and the equations defining the time averaged data sets to recover the original data encoded onto the optical signal.

4. The method according to claim 3 , wherein
the first and subsequent iterations employ a set of digital signal processing equations defining all possible combinations of N received symbols to N bits of the original signal.

5. The method according to claim 1 , wherein
digitally processing the N streams of symbols comprises employing a set of digital signal processing equations defining all possible combinations of N received symbols to N bits of the original signal.

6. The method according to claim 1 , wherein
optical splitting and delaying the received optical signal employs at least one of a monolithic integrated optical circuit, a hybrid integrated optical circuit, and a free space optical assembly.

7. The method according to claim 1 , wherein
the steps of optically splitting, time averaging, gating and digitally processing the received optical signal at least one of reduce error propagation within an optical receiver exploiting the method and provide an alternate precoding method for polybinary signal transmission.

8. A system comprising:
an input port for receiving an optical input amplitude modulated at a predetermined data rate X Gb/s;
an optical splitter for optically splitting the received optical signal into N optical channels at X Gb/s and coupling each channel to a predetermined optical detector, wherein the optical signal at each optical detector differs in time relative to the optical signal at an adjacent optical detector by that equivalent to a single bit at X Gb/s through optical delays lines at least one of forming part of the optical splitter and coupled to the optical splitter;
a plurality of front end electronic circuits each connected to an optical detector, each front end electronic circuit:
time averaging the output of each optical detector for a duration equivalent to N bits at X Gb/s;
gating the time averaged signal from each optical detector at a rate of X/N Gb/s to generate N streams of symbols; and

a digital processor for digitally processing the N streams of symbols to generate the original X Gb/s data.

9. The method according to claim 8 , wherein
time averaging the output of an optical detector comprises employing a resistive—capacitive network between the output of the optical detector and a transimpedance amplifier for converting a time averaged photocurrent to voltage; and
gating the time averaged photocurrent comprises activating a switch disposed between the resistive—capacitive network and the transimpedance amplifier.

10. The method according to claim 8 , wherein
the digital processor executes a process comprising:
initializing the processing with a first set of gated time averaged data;
establishing a first iteration with the next gated time average data and deducing an original unknown N bits from the N symbols and their equations defining each time averaged data set to a block of received N bits;
continuing to iterate using the currently known input bits and the equations defining the time averaged data sets to recover the original data encoded onto the optical signal.

11. The system according to claim 8 , wherein
the optical splitter, the optical delay lines, and the photodetectors each form part of an optical component; and
the optical component employs at least one of a monolithic integrated optical circuit, a hybrid integrated optical circuit, and a free space optical assembly.

12. A system comprising:
an input port for receiving an optical input amplitude modulated at a predetermined data rate X Gb/s;
a pre-processing circuit for processing an optical signal received at the input port, the processing for generating N channels from the received optical signal, wherein each channel is time averaged for a duration equivalent to N bits at X Gb/s with an equivalent data rate of X/N Gb/s and time delayed by a predetermined number of bits of the X Gb/s input signal; and
a processing circuit coupled to the pre-processing circuit for receiving the N channels of time delayed and averaged data and generating in dependence upon these the original X Gb/s data.

13. The system according to claim 12 , wherein
the pre-processing circuit comprises:
an optical splitter for generating the N channels;
a plurality of optical delay lines for generating the required delays in combination with the optical splitter; and
N photodetectors for generating N electrical signals from the N optical signals generating by the optical splitter and the plurality of optical delay lines.

14. The system according to claim 13 , wherein
the pre-processing circuit further comprises:
a plurality of front end electronic circuits each connected to an optical detector, each front end electronic circuit:
time averaging the output of each optical detector for a duration equivalent to N bits at X Gb/s; and
gating the time averaged signal from each optical detector at a rate of X/N Gb/s to generate N streams of symbols.

15. The system according to claim 12 , wherein
the pre-processing circuit comprises:
an optical splitter for generating the N channels;
N photodetectors for generating N electrical signals from the N optical signals generated by the optical splitter; and
a plurality of electrical delay lines electrically coupled to the N photodetectors for generating the required delays.

16. The system according to claim 15 , wherein
the pre-processing circuit further comprises:
a plurality of front end electronic circuits each disposed either prior to or after an electrical delay line, each front end electronic circuit:
time averaging the output of each optical detector for a duration equivalent to N bits at X Gb/s; and
gating the time averaged signal from each optical detector at a rate of X/N Gb/s to generate N streams of symbols.

17. The system according to claim 12 , wherein

Assignees

• The Royal Institution For The Advancement Of Learning/Mcgill Univ
• Transfert Plus Soc En Commandite
• The Royal Institution For The Advancement Of Learning/ Mcgill Univ

Inventors

• Liboiron-Ladouceur Odile
• Hai Md Shafiqul
• Menard Michael

Classifications

• G01J1/44

  Electric circuits {(for command of an exposure part G03B7/02)} · CPC title

• H04B10/60 Primary

  Receivers · CPC title

• G01J1/46 Primary

  using a capacitor · CPC title

• H04B10/66

  Non-coherent receivers, e.g. using direct detection · CPC title