High-speed serial-to-parallel and analog-to-digital conversion

• US 20010020908A1
• Filed: 04/16/2001
• Published: 09/13/2001
• Est. Priority Date: 09/30/1997
• Status: Active Grant

• Current Assignee: The Trustees of Princeton University (Princeton University)
• Original Assignee: The Trustees of Princeton University (Princeton University)
• Inventors: Prucnal, Paul R.
• Granted Patent: US 6,433,715 B2
• Time in Patent Office: Days
• US Class Current: 341/137
• CPC Class Codes: H03M 1/121 Interleaved, i.e. using multiple converters or converter parts for one channel
• CPC Class Codes: H04L 7/0075 with photonic or optical means

Abstract

An optical-to-electrical converter includes an input port configured to receive an optical signal. The converter further includes a splitter configured to split the received I optical signal into a plurality of optical signals. An optical stage has a plurality of parallel stages, and each parallel stage receives a corresponding one of the plurality of identical signals and outputs a corresponding one of a plurality of sampled optical signals within a corresponding sampling window. A plurality of delay circuits receive a clock signal having a plurality of clock pulses separated by a clock period. The delay circuits respectively output a plurality of control pulses at a plurality of delayed timings with respect to each clock pulse of the clock signal. An electrical stage receives the plurality of sampled optical signals and processes the optical signals at a sampling rate corresponding to the clock period of the clock signal.

Claims

1. An optical-to-electronic convertor, comprising:

an input port, which receives an optical signal that is to be sampled;

an optical sampler stage including at least one high-speed optical shutter, which samples the optical signal at a first sampling rate by opening and closing the at least one high-speed optical shutter and which provides a plurality of sampled optical signals as a result thereof, the optical sampler stage including a plurality of parallel channels, each different channel providing a different one of said plurality of sampled optical signals, the optical sampler stage including a splitter for splitting the optical signal into a plurality of identical optical signals prior to the sampling at the first sampling rate; and

an electronic analog-to-digital converter stage, which converts the plurality of sampled output signals into a plurality of digital signals, the electronic analog-to-digital converter stage performing the converting at a second sampling rate slower than the first sampling rate.

2. The optical-to-electronic converter as recited in

claim 1

, wherein the electronic analog-to-digital converter stage comprises a single analog to digital converter which receives the outputs from each of the plurality of parallel channels in a time sequential manner.

3. The optical-to-electronic converter as recited in

claim 1

, wherein the electronic analog-to-digital converter stage comprises a plurality of electronic converters disposed in a plurality of parallel channels, wherein the plurality of channels of the electronic analog to digital converter stage respectively receive the sampled optical signals output from the plurality of parallel channels of the optical sampler stage.

4. The optical-to-electronic converter as recited in

claim 1

, further comprising a conversion stage disposed between the optical sampler stage and the electronic analog-to-digital converter stage, the conversion stage performing a conversion of the plurality of sampled optical signals into a plurality of electronic sampled signals.

5. The optical-to-electronic converter as recited in

claim 4

, wherein the conversion stage includes a plurality of photodetectors respectively disposed in the plurality of parallel channels of the optical sampler stage.

6. The optical-to-electronic converter as recited in

claim 5

, wherein the optical sampler stage comprises:

a plurality of terahertz optical asymmetric demultiplexer assemblies (TOADs) respectively disposed in the plurality of parallel channels of the optical sampler stage and each configured to sample a corresponding one of the plurality of identical optical signals at different times,

wherein the plurality of detectors are respectively disposed between the plurality of TOADs and the electronic analog-to-digital converter stage.

7. The optical-to-electronic converter as recited in

claim 3

, wherein the plurality of parallel channels of the optical sampler stage corresponds in number to n, and

wherein n multiplied by the second sampling rate is approximately equal to the first sampling rate.

8. An optical to electronic converter, comprising:

a first input port configured to receive an analog optical waveform;

a splitter connected to the first input port and configured to split the analog optical waveform into a plurality of approximately identical waveforms;

a second input port configured to receive a clock signal having a predetermined clock period;

a delay circuit configured to receive the clock signal and to output a plurality of delayed clock signals each having a different delay with respect to other of the delayed clock signals;

a plurality of terahertz optical asymmetric demultiplexers configured to respectively receive the plurality of approximately identical waveforms on an input port thereof, and configured to receive a corresponding one of the plurality of delayed clock signals on a control port thereof, each of the plurality of terahertz optical asymmetric demultiplexers having an output port for outputting the corresponding one of the plurality of approximately identical waveforms within a fixed time period;

a plurality of photodetectors, each different photodetector connected to a different one of said output ports of the plurality of terahertz optical asymmetric demultiplexers and configured to convert an input optical signal into an output electrical signal; and

a plurality of electrical analog-to-digital converters respectively connected to the output ports of the plurality of terahertz optical asymmetric demultiplexers and configured to perform an analog-to-digital conversion of the corresponding electrical signal into a digital signal,

wherein a number corresponding to said plurality of electrical analog-to-digital converters is a value such that a conversion time of the plurality of electrical analog-to-digital converters divided by the number of said plurality of electrical analog-to-digital converters is approximately equal to the time period of the plurality of terahertz optical asymmetric demultiplexers.

9. A method of optical sampling, comprising the steps of:

receiving an optical signal that is to be sampled;

splitting the received optical signal into a plurality of approximately identical optical signals; and

respectively providing the approximately identical optical signals to a plurality of channels of an optical stage; and

sampling, at the optical stage, the optical signal at a first sampling rate by opening and closing a high-speed optical shutter and providing a plurality of sampled optical signals as a result thereof, each of the plurality of parallel channels of the optical stage providing a different one of said plurality of optical signals.

10. The method as recited in

claim 9

, further comprising the step of converting the plurality of sampled optical signals into a plurality of electronic sampled signals.

11. The method as recited in

claim 10

, further comprising the steps of:

splitting the received optical signal into a plurality of approximately identical optical signals; and

respectively providing the approximately identical optical signals to a plurality of channels of the optical stage so as to perform the sampling step.

12. An analog optical sampler, comprising:

a first input port that is capable of receiving an analog optical waveform that is to be sampled;

a second input port that is capable of receiving a clock signal;

at least one Terahertz Optical Asymmetric Demultiplexer (TOAD) that is configured to receive the analog optical waveform and the clock signal; and

an output port, from which is output a sample of the analog optical waveform, the sample being provided to the output port based on an output of at least one TOAD;

wherein the analog optical waveform is sampled when said TOAD is triggered by the clock signal.

13. The analog optical sampler as recited in

claim 12

, wherein at least one of the first input port, the second input port, and the output port includes an optical waveguide or an optical fiber.

14. The analog optical sampler as recited in

claim 13

, wherein distinct polarizations or colors are used to multiplex the first and second input ports on a same optical waveguide or optical fiber.

15. The analog optical sampler as recited in

claim 12

, wherein at least one TOAD includes a Mach-Zehnder interferometer.

16. An optical sampler system, comprising:

a first input port, which receives an optical analog waveform that is to be sampled;

a second input port, which receives an optical clock signal at a clock rate;

a plurality of optical samplers, which produce a plurality of sampled optical waveforms from said optical analog waveform at a rate dependent on said clock signal, at least one of said plurality of optical samplers including a Terahertz Optical Asymmetric Demultiplexer (TOAD); and

a plurality of output ports, which output said plurality of sampled optical waveforms.

17. An optical sampler system, comprising:

a plurality of first input ports for receiving an optical analog waveform;

a plurality of second input ports for receiving an optical clock signal at a clock rate;

a plurality of optical sampler nodes for respectively producing a plurality of sampled optical waveforms from said optical analog waveform at a rate dependent on said clock signal;

a plurality of output ports for respectively outputting said plurality of sampled optical waveforms;

a first optical distribution network for replicating and delivering a plurality of copies of said optical clock signal; and

a second optical distribution network for replicating and delivering a plurality of copies of said optical analog waveform, said second optical distribution network including delay lines of differing optical lengths so as to provide each of said plurality of optical sampler nodes with a substantially unique timeslice of said analog optical waveform upon receipt of a corresponding one of said plurality of copies of said optical clock signal.

18. The optical sampler system as recited in

claim 17

, wherein said plurality of copies of said optical clock signal are delayed with respect to each other by a preset delay amount.

19. The optical sampler system as recited in

claim 17

, wherein at least one of said plurality of optical sampler nodes includes at least one Terahertz Optical Asymmetric Demultiplexer.

20. The optical sampler system as recited in

claim 17

, further comprising an optical-to-electronic converter stage connected to at least one of said plurality of output ports, and configured to receive said sampled optical waveform and to convert said sampled optical waveform into an electronic waveform.

21. The optical sampler system as recited in

claim 20

, further comprising an analog-to-digital converter stage connected to said optical-to-electronic converter stage, and configured to convert said electronic waveform into a digital signal.

22. The optical sampler system as recited in

claim 21

, wherein said plurality of optical sampler nodes produce said plurality of sampled waveforms on a plurality of parallel channels, respectively, the plurality of parallel channels corresponding to n in number, n being an integer greater than one,

wherein n multiplied by a first sampling rate of the conversion by said plurality of optical sampler nodes is approximately equal to a second sampling rate of said analog-to-digital converter stage.

23. The optical sampler system as recited in

claim 17

, wherein distinct signal levels of at least one of said copies of said optical clock signal and said copies of said optical analog waveform through distinct paths in said first and second distribution networks are provided as correction signals used to correct a calibration of subsequent magnitude measurements of said optical sampler system.

24. An optical sampler system, comprising:

a plurality of high-speed optical shutters, each having a signal input port capable of receiving an optical input signal, a trigger input port capable of receiving an optical clock signal, and an output port;

a first optical distribution network, which receives an optical clock signal and delivers a corresponding optical clock signal to the trigger input port of each optical shutter; and

a second optical distribution network, which receives an optical analog waveform and delivers a corresponding optical analog waveform to the signal input port of each optical shutter;

wherein, for each optical shutter, the corresponding optical clock signal is synchronized with the corresponding optical analog waveform to open and close a gating window during which the optical shutter produces an optical waveform sample on its output port.

25. The optical sampler system of

claim 24

, wherein the high-speed optical shutter is a TOAD.

26. The optical sampler system of

claim 24

, wherein the high-speed optical shutter is open for a duration in the range from about 0.01 psec to about 100 psec.

27. The optical sampler system of

claim 24

, wherein the optical waveform sample produced by each optical shutter is substantially unique.

28. The optical sampler system of

claim 24

, wherein the second optical distribution network comprises delay lines of differing optical lengths.

29. The optical sampler system of

claim 24

, wherein the first optical distribution network comprises delay lines of differing optical lengths.

30. The optical sampler system of

claim 24

, further comprising an optical-to-electronic converter stage connected to the output ports of the plurality of high-speed optical shutters.

31. The optical sampler system of

claim 24

, wherein the first and second optical distribution networks each include an optical path over which correction signals are provided to correct a calibration of subsequent magnitude measurements of the optical waveform samples.

32. A method of sampling an optical signal, comprising the steps of:

receiving a continuous optical analog signal having an intensity that may be any value within two predetermined intensity limits;

receiving an optical triggering signal;

providing the continuous optical analog signal to an optical shutter;

providing the optical triggering signal to the optical shutter; and

outputting from the optical shutter, a discrete sample segment of the continuous optical analog signal.

33. The method of

claim 32

, wherein the optical shutter is a high-speed optical shutter.

34. The method of

claim 33

, wherein the high-speed optical shutter is a TOAD.

35. The method of

claim 32

, wherein the duration of the discrete sample segment is within arange of about 0.01 psec to about 100 psec.