High power multiwavelength light source

Details High power multiwavelength light source High power multiwavelength light source

1998-02-18

2001-02-27

Moskowitz, Nelson (Department: 3662)

Optical: systems and elements

Optical amplifier

Optical fiber

C359S199200, C359S199200, C359S333000, C359S347000, C372S006000

Reexamination Certificate

active

06195200

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to light sources and, in particular, to a high power multiwavelength light source particularly useful in connection with wavelength division multiplexed (WDM) optical communication systems.
BACKGROUND OF THE INVENTION
Multiwavelength light sources are highly useful for testing WDM optical communication systems and components and as light sources for such systems. A multiwavelength light source is a light source which emits light in a plurality of spectrally spaced apart wavelength channels. In WDM optical communications system, an optical fiber simultaneously carries many different communications channels in light of respectively different wavelengths. Typically 8, 16 or 32 different wavelength signals propagate through the system. In testing WDM systems, components and test equipment, test sources are needed which produce light in the specific channels of the systems.
Typical multiwavelength sources utilize separate sources, such as ECL lasers, for each channel. The separate channels are generated one at a time and then combined to generate a multiwavelength source. This approach is expensive and inefficient.
Researchers have tried to generate multiwavelength sources by creating several very short lasers in a single piece of erbium doped fiber (EDF). This approach has proved inefficient and produces unstable lasers.
Others have used polarization inhomogeniety or spectral inhomogeniety in combination with wavelength selective elements to make an EDF laser with multiple laser wavelengths. But no truly stable, easily manufactured source has been found.
In yet other attempts, broadband light has been generated in EDF by amplified spontaneous emission (ASE) and, by means of filters, divided into several spectral bands. However, such sources produce poor power output in each channel because much of the power generated in the ASE source is between channels and is lost. Accordingly there is a need for an efficient, inexpensive multiwavelength light source.
SUMMARY OF THE INVENTION
In accordance with the invention, a multiwavelength light source comprises a length of optical waveguide amplifier, a multiwavelength reflector for reflecting a plurality of different spectrally separated wavelengths optically coupled to one side of the amplifier and a low reflection output coupled to the other side. A broadband source is provided for passing broadband light to the multiwavelength reflector. In the preferred embodiment, the reflector is a plurality of reflective Bragg gratings, the waveguide amplifier is a length of rare-earth doped fiber (e.g. EDF) and the broadband source is the amplifier pumped to generate ASE. In operation, broadband light is transmitted to the gratings. Light of wavelength channels corresponding to the reflection wavelengths of the gratings is reflected back through the amplifier for further amplification before it arrives at the output. Optionally one or more transmission filters can be disposed between the reflector and the amplifier (or at the output) ASE source to control the relative magnitudes of the selected channels.


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DeSurvire E.; Erbium Doped Fiber Amplifiers, Publ. John Wiley & Sons, ISBN 0-471-58977-2, pp. 318, 319, 462, 463, 514, 515, 1994.

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