Demultiplexing and clock-recovery circuit

• US 6,556,323 B1
• Filed: 02/16/2000
• Issued: 04/29/2003
• Est. Priority Date: 02/17/1999
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Raybon, Gregory, Mikkelsen, Benny Peter
• Primary Examiner(s): Pascal, Leslie
• Assistant Examiner(s): Payne, David C.
• Application Number:
  US09/505,328
• Time in Patent Office: 1,168 Days
• Field of Search: 359/158, 359/154, 359/187, 359/135, 359/138, 359/180, 359/181
• US Class Current: 398/154
• CPC Class Codes: H04B 10/66 Non-coherent receivers, e.g. using direct detection
• CPC Class Codes: H04B 10/67 Optical arrangements in the receiver
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04L 7/0075 with photonic or optical means

Abstract

An optical element for simultaneously retrieving the tributary data rate and the clock frequency from the line rate of an OTDM signal. The demultiplexing and clock recovery principle is based on injection locking of a high-Q-filtered and high gain loop with a variable phase delay and an EA-modulator with high non-linear response, i.e., absorption verses applied voltage. A modulator that is preferably an EA-modulator, an amplifier preferably an erbium doped fiber amplifier (“EDFA”), a base band receiver, an electronic amplifier, a high-Q filter, and a variable phase delay are arranged in a loop to provide an oscillator for simultaneously retrieving tributary data rate and clock frequency.

Claims

1. A demultiplexing and clock frequency-recovery circuit comprising:

a non-linear modulator for providing a tributary signal from a received signal;

an optical amplifier coupled to the non-linear modulator to amplify the received signal;

a baseband receiver coupled to the optical amplifier,

the baseband receiver for converting the received signal into an electric signal;

an amplifier coupled to the baseband receiver for amplifying the received signal;

a high-Q filter coupled to the amplifier for filtering a signal of selected frequency range; and

a variable phase delay coupled to the high-Q filter and the non-linear modulator, the variable phase delay for adjusting phase in the filtered signal of selected frequency range and feeding the phase adjusted filtered signal back to the non-linear modulator, wherein the baseband signal frequency and clock frequency are recovered.

2. The circuit of claim 1, wherein the optical amplifier includes an erbium doped fiber amplifier.

3. The circuit of claim 1, wherein the non-linear modulator includes an electro-absorption modulator.

4. The circuit of claim 1, wherein the non-linear modulator includes an electro-optic modulator.

5. The circuit of claim 1, wherein the non-linear modulator includes a semiconductor optical amplifier.

6. The circuit of claim 1, wherein the non-linear modulator includes a plurality of non-linear modulators arranged as a cascade of modulators.

7. The circuit of claim 6, wherein a harmonic of a tributary frequency signal is fed back to one of the plurality of non-linear modulators.

11. The circuit of claim 7, wherein the non-linear modulator includes a semiconductor optical amplifier.

12. The circuit of claim 7, wherein at least one other non-linear modulator of the plurality of non-linear modulator include electro-absorption modulators.

13. The circuit of claim 7, wherein a harmonic of a tributary frequency signal is fed back to the non-linear modulators.

8. A demultiplexing and clock-recovery circuit comprising:

a non-linear modulator for providing a tributary signal from a received signal;

an optical amplifier coupled to the non-linear modulator to amplify the received signal;

a baseband receiver coupled to the optical amplifier;

an amplifier coupled to the amplifier for extracting a signal of selected frequency range from the received signal; and

a variable phase delay coupled to the high-Q filter, the variable phase delay further coupled to the non-linear modulator, the variable phase delay for correcting phase of the signal output from the high-Q filter and feeding back the phase corrected signal to the non-linear modulator; and

a plurality of phase delay and second non-linear modulator pair coupled to the high-Q filter for outputting a plurality of tributary data signals.

9. The circuit of claim 8, wherein the first amplifier includes an erbium doped fiber amplifier.

10. The circuit of claim 8, wherein the non-linear modulator includes an electro-absorption modulator.