Modulation format adjusting optical transponders

• US 6,256,127 B1
• Filed: 03/06/2000
• Issued: 07/03/2001
• Est. Priority Date: 05/29/1997
• Status: Expired due to Term

• Current Assignee: Ciena Corporation
• Original Assignee: Ciena Corporation
• Inventors: Taylor, Michael G.
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/519,828
• Time in Patent Office: 484 Days
• Field of Search: 359/124, 359/125, 359/173, 359/110, 359/279
• US Class Current: 398/9
• CPC Class Codes: H04B 10/29 Repeaters
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems
• CPC Class Codes: H04J 14/0305 in end terminals

Abstract

The present invention provides a modulation format adjusting optical transponder for receiving an incident optical signal of a first modulation format and outputting an optical signal having a different modulation format. The transponder includes an optical-to-electrical conversion element configured to receive an information-bearing optical signal having a first modulation format and output an electrical signal corresponding to information from the incident optical signal. The transponder includes a laser for outputting an optical carrier signal at a selected wavelength and a modulator communicating with the optical-to-electrical conversion element and with the laser. The modulator places the information from the incident optical signal onto the optical signal output by the laser, creating a modulated optical output signal having a second modulation format different from the first modulation format. Advantageously, the optical system of the present invention can take optical signals in a common modulation format, such as amplitude modulation, and output optical signals in a power-flat modulation format, such as frequency shift key (FSK) modulation. The modulation format adjusting optical transponders of the present invention can be used as remodulators for wavelength division multiplexed optical systems.

Claims

1. A modulation format adjusting optical transponder comprising:

an optical-to-electrical conversion element configured to receive a single first optical signal having a first modulation format and carrying associated data, the optical-to-electrical conversion element outputting an electrical signal corresponding to said associated data of said first optical signal;

a laser; and

a modulation circuit communicating with the optical-to-electrical conversion element and with the laser said modulation circuit being configured to control an output of said laser to transmit a single second optical signal carrying the associated data of said first optical signal, said second optical signal being modulated in accordance with a second modulation format different than said first modulation format such that said first optical signal having said first modulation format is retransmitted as said second optical signal having said second modulation format, there being a one-to-one correspondence between said first optical signal and said second optical signal.

2. A modulation format adjusting optical transponder as recited in claim 1 wherein the first modulation format is amplitude modulation and the second modulation format is frequency shift key modulation.

3. A modulation format adjusting optical transponder as recited in claim 1 wherein the first modulation format is amplitude modulation and the second modulation format is polarization shift key modulation.

4. A modulation format adjusting optical transponder as recited in claim 1 wherein the first modulation format is amplitude modulation and the second modulation format is chirped amplitude modulation comprising amplitude and phase modulation.

5. A wavelength division multiplexed optical communication system comprising:

a plurality of optical remodulators, each of which being configured to receive a respective one of a first plurality of optical signals, and outputting a respective one of a second plurality of optical signals, there being a one-to-one correspondence between each of said first plurality of optical signals and each of said second plurality of optical signals, each of the remodulators comprising;

an optical-to-electrical conversion element for receiving a respective one of a first plurality of optical signals and outputting an electrical signal corresponding to data carried by said respective one of said first plurality of optical signals;

a laser;

a modulation circuit communicating with the optical-to-electrical conversion element and with the laser and being configured to output a respective one of said second plurality of optical signals, each of which carrying said data carried by said respective one of said first plurality of optical signals and being modulated in accordance with a modulation format different than a modulation format associated with at least one of said first plurality of optical signals such that each of said first plurality of optical signals is retransmitted as a corresponding one of said second plurality of optical signals;

an optical waveguide;

an optical combining element being configured to receive said second plurality of optical signals produced by the remodulators, the optical combining element being configured to combine the second plurality of optical signals onto the optical waveguide;

a plurality of optical selectors optically communicating with the optical waveguide, each optical selector configured to select one or more of said second plurality of optical signals; and

a plurality of optical receivers optically communicating with the optical selectors.

6. A wavelength division multiplexed optical communication system as recited in claim 5 wherein the first modulation format is amplitude modulation and the second modulation format is frequency shift key modulation.

7. A wavelength division multiplexed optical communication system as recited in claim 5 wherein the first modulation format is amplitude modulation and the second modulation format is polarization shift key modulation.

8. A wavelength division multiplexed optical communication system as recited in claim 5 wherein the first modulation format is amplitude modulation and the second modulation format is chirped amplitude modulation comprising amplitude and phase modulation.