Optical transmitter

• US 20070110453A1
• Filed: 03/01/2006
• Published: 05/17/2007
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamamoto, Tsuyoshi, Akiyama, Suguru
• Granted Patent: US 7,738,794 B2
• Time in Patent Office: Days
• US Class Current: 398/182
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02F 1/3519 of Sagnac type, i.e. nonlinear optical loop mirror [NOLM]
• CPC Class Codes: H01S 5/0078 for frequency filtering
• CPC Class Codes: H04B 10/25 Arrangements specific to fibre transmission
• CPC Class Codes: H04B 10/503 Laser transmitters
• CPC Class Codes: H04B 10/504 using direct modulation
• CPC Class Codes: H04B 10/58 Compensation for non-linear transmitter output

Abstract

In an optical transmitter comprising a directly modulated laser and a wavelength filter provided on a post-stage of the directly modulated laser, the wavelength filter has a modulated light input port for inputting modulated light output from the directly modulated laser, a filter transmitted light output port for outputting light having a wavelength included in a filter transmission band among the modulated light as filter transmitted light, and a filter cutoff light output port provided separately from the modulated light input port and the filter transmitted light output port and outputting light having a wavelength included in a filter cutoff band among the modulated light as filter cutoff light, and the peak of the filter transmission band is set on a shorter-wave side from the peak of the spectrum of modulated light output from the directly modulated laser.

Claims

1. An optical transmitter comprising:

a directly modulated laser; and

a wavelength filter provided on a post-stage of said directly modulated laser,

wherein, said wavelength filter has;

a modulated light input port connected to said directly modulated laser and inputting modulated light output from said directly modulated laser;

a filter transmitted light output port connected to an optical coupling system and outputting light having a wavelength included in a filter transmission band among said modulated light as filter transmitted light; and

a filter cutoff light output port provided separately from said modulated light input port and said filter transmitted light output port and outputting light having a wavelength included in a filter cutoff band among said modulated light as filter cutoff light, and

wherein the peak of said filter transmission band is set on a shorter-wave side from the peak of the spectrum of modulated light output from said directly modulated laser.

2. The optical transmitter according to claim 1, wherein said directly modulated laser and said wavelength filter are integrally formed on the same substrate.

3. The optical transmitter according to claim 1, wherein said directly modulated laser and said wavelength filter are integrated in a hybrid manner on a planer lightwave circuit substrate formed of one of silica glass, polymer, silicon, dielectric, and semiconductor materials.

4. The optical transmitter according to claim 1, comprising a light absorption region for absorbing filter cutoff light output from said filter cutoff light output port.

5. The optical transmitter according to claim 1, comprising a temperature control device capable of controlling the temperature of said directly modulated laser and/or said wavelength filter.

6. The optical transmitter according to claim 1, further comprising:

a monitor photodetector for detecting filter cutoff light output from said filter cutoff light output port; and

a control circuit for controlling said directly modulated laser based on the power of filter cutoff light detected by said monitor photodetector.

7. The optical transmitter according to claim 5, further comprising:

a monitor photodetector for detecting filter cutoff light output from said filter cutoff light output port; and

a control circuit for controlling said temperature control device based on the power of filter cutoff light detected by said monitor photodetector.

8. The optical transmitter according to claim 1, wherein said wavelength filter is a ring resonator type wavelength filter formed of a ring resonator.

9. The optical transmitter according to claim 1, wherein said wavelength filter is a Mach-Zehnder type wavelength filter formed of a Mach-Zehnder interferometer.

10. The optical transmitter according to claim 9, wherein said Mach-Zehnder type wavelength filter is a diffraction grating mounted Mach-Zehnder type wavelength filter that mounts a diffraction grating on said Mach-Zehnder interferometer.

11. The optical transmitter according to claim 9, wherein said Mach-Zehnder type wavelength filter is a ring resonator mounted Mach-Zehnder type wavelength filter that mounts a ring resonator on said Mach-Zehnder interferometer.

12. The optical transmitter according to claim 1, wherein said wavelength filter is composed such that the change rate of the intensity of said filter transmitted light with respect to the wavelength is in a range of 100 dB/nm to 300 dB/nm at a wavelength at which the intensity of said filter transmitted light falls by 3 dB.