Optical transmission system

• US 5,671,075 A
• Filed: 10/25/1995
• Issued: 09/23/1997
• Est. Priority Date: 06/25/1992
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Synchronous Communications, Inc.
• Inventors: Gysel, Hermann, Ramachandran, Mani
• Primary Examiner(s): PASCAL, LESLIE C
• Application Number:
  US08/547,916
• Time in Patent Office: 699 Days
• Field of Search: 359/179-181, 372/96
• US Class Current: 398/147
• CPC Class Codes: G02F 1/0121 Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
• CPC Class Codes: H04B 10/2537 due to scattering processes, e.g. Raman or Brillouin scattering
• CPC Class Codes: H04B 10/291 in which processing or amplification is carried out without conversion of the main signal from optical form
• CPC Class Codes: H04B 10/2912 characterised by the medium used for amplification or processing

Abstract

An optical transmission system is provided comprising a method and apparatus for cancelling noise in the output from a light source for broadening the line width of a light source so as to increase stimulated Brillouin scattering threshold in a standard single mode fiber with a dispersion null at 1310 nm and for using a linearized external modulator to modulate the amplified output of a distributed feedback laser providing an output at 1550 nanometers for use on a standard single mode fiber optic cable with a dispersion null at 1310 nm.

Claims

1. An optical transmission system comprising:

a distributed feedback (DFB) laser for providing coherent radiation;

first amplifier for amplifying radiation from the DFB;

linearized modulating means responsive to amplified radiation from the first amplifier for modulating the amplified radiation; and

second amplifier for amplifying modulated radiation from the linearized modulating means wherein the first and second aplifiers compensate for insertion loss in the optical transmission system caused by the linearized modulating means.

2. An optical transmission system according to claim 1 wherein said linearized modulating means has a depth of modulation of at least 4 percent.

3. A method of transmitting optical signals comprising the steps of:

providing coherent radiation from a distributed feedback (DFB) laser;

amplifying the radiation from the DFB laser;

modulating the amplified radiation using a linearized modulating means; and

amplifying the modulated radiation to compensate for losses caused by the linearized modulating means.

4. A method according to claim 3 wherein said linearized modulating means has a depth of modulation of at least 4 percent.

5. An optical transmission system, comprising:

light source that generates coherent radiation;

first amplifier that generates amplified radiation by amplifying the coherent radiation from the light source;

linearized modulator that generates modulated radiation by modulating the amplified radiation with an electrical modulation signal;

second amplifier that amplifies the modulated radiation for transmission over an optical fiber wherein the first and second amplifiers compensate for insertion losses caused by the linearized modulator.

6. The optical transmission system of claim 5, wherein the light source comprises a laser.

7. The optical transmission system of claim 6, wherein the laser comprises a distributed feedback laser.

8. The optical transmission system of claim 5, wherein the first amplifier comprises an erbium doped fiber amplifier.

9. The optical transmission system of claim 5, wherein the second amplifier comprises an erbium doped fiber amplifier.

10. The optical transmission system of claim 5, wherein the linearized modulator has a relatively high insertion loss in comparison to nonlinear modulators.

11. The optical transmission system of claim 10, wherein the first and second amplifiers compensate for the relatively high insertion loss.

12. The optical transmission system of claim 10, wherein the linearized modulator provides a relatively high modulation depth in comparison to nonlinear modulators.

13. The optical transmission system of claim 5, wherein the optical fiber comprises a single mode fiber with a dispersion null at 1310 nanometers.

14. The optical transmission system of claim 13, wherein the first amplifier is an external erbium doped fiber amplifier that prevents second order (CSO) distortions in the single mode optical fiber.