Optical modulator providing independent control of attenuation and spectral tilt

• US 6,002,513 A
• Filed: 06/22/1998
• Issued: 12/14/1999
• Est. Priority Date: 06/22/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Goossen, Keith Wayne, Knox, Wayne Harvey
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): BURKE, MARGARET A
• Application Number:
  US09/102,514
• Time in Patent Office: 540 Days
• Field of Search: 359/124, 359/134, 359/181, 359/223, 359/224, 359/290, 359/291, 359/295, 359/318, 359/341
• US Class Current: 359/291
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 6/264 with optical elements between opposed fibre ends which perform a function other than beam splitting having lens focusing means G02B6/32; utilising prism or grating G02B6/34
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/3833 Details of mounting fibres in ferrules; Assembly methods; Manufacture
• CPC Class Codes: H04J 14/02 Wavelength-division multiplex systems

Abstract

An optical modulator comprises at least two optically coupled MARS modulators, at least one having positive spectral tilt and at least one having negative spectral tilt. Both tilt and attenuation can be independently controlled by adjusting the air gaps of the constituent modulators. Preferred designs present linear spectral tilt.

Claims

1. An optical modulator for providing independent control of attenuation and spectral tilt across an optical signal comprising:

first and second micromechanical modulators, each of the first and second micromechanical modulators including a Fabry-Perot optical cavity between an optical membrane and a substrate and employing voltage-controlled movement of the membrane in relation to the substrate, the first micromechanical modulator having a positive reflectivity vs. wavelength spectral tilt across said signal and the second micromechanical modulator having a negative reflectivity vs. wavelength spectral tilt across said signal wherein the second micromechanical modulator is optically coupled to the first micromechanical modulator.

2. The modulator of claim 1 wherein said first and second MARS modulators are optically coupled by a length of optical fiber.

3. The modulator of claim 1 wherein said first and second MARS modulators are optically coupled by a reflector.

4. The modulator of claim 1 wherein said membrane comprises a plurality of layers of different material.

5. The modulator of claim 4 wherein the thicknesses of different layers of said plurality are chosen to produce a linear spectral tilt across said signal.

6. The modulator of claim 1 wherein said substrate comprises silicon and said membrane comprises layers of silicon nitride and polysilicon.

7. A WDM optical communications system comprising:

a WDM transmitter;

an optical fiber for receiving a WDM signal from said transmitter;

an optical amplifier for amplifying a signal on said fiber; and

optically coupled to said fiber, an optical modulator for providing independent control of attenuation and spectral tilt across the WDM signal comprising first and second micromechanical modulators, each of the first and second micromechanical modulators including a Fabry-Perot optical cavity between an optical membrane and a substrate and employing voltage-controlled movement of the membrane in relation to the substrate, the first micromechanical modulator having a positive reflectivity vs. wavelength spectral tilt across the WDM signal and the second micromechanical modulator having a negative reflectivity vs. wavelength spectral tilt across said WDM signal, the second micromechanical modulator being optically coupled to the first micromechanical modulator.