A filtering device for a cross-wavelength wavelength division multiplexer

Abstract

The invention provides a filtering device of a cross-wavelength wavelength division multiplexer. The filtering device is composed of a light split device, an optical path difference introducing device, a half-wave plate and a light combination device. The light split device and the light combination device are respectively a polarization splitting prism formed by sequentially connecting a first right-angled trapezoid-shaped birefringent crystal wedge angle piece, a flat glass piece and a second right-angled trapezoid-shaped birefringent crystal wedge angle piece. The optical path difference introducing device is composed of two flat optical pieces, wherein the temperature coefficient of the refractive index of at least one flat optical piece is a negative value. The filtering device has better temperature stability and higher reliability and can greatly reduce the sizes of optical components and reduce cost.

Description

technical field [0001] The invention relates to an optical passive device in an optical and optical fiber communication system, in particular to a filter unit structure of a cross wavelength division multiplexer. Background technique [0002] DWDM is an optical passive device that simultaneously combines and transmits light of many different wavelengths in the same optical fiber. As people's demand for information capacity and transmission speed continues to increase, DWDM is also being continuously developed and improved by people. Among them, the Interleaver device is a DWDM demultiplexing device with excellent performance. The Interleaver device is a cross-wavelength multiplexer used in the field of optical fiber communication. It includes an input port and two output ports. Signals with a frequency interval of Δf in adjacent channels are input from the input port and separated into frequency differences after passing through the Interleaver. The odd and even groups of s...

AI Technical Summary

Problems solved by technology

But they all have defects. For example, the Mach-zehnder interferometer needs to precisely control the length of two optical fibers, and the process requirements are very high.

The Fabry-Perot interferometer uses a resonant cavity to improve the line width, the effect is limited, and the contrast is also limited due to the poor dispersion of the etalon structure

The crystal type is more costly, larger and more expensive

[0003] At present, there are many patents on the filter device of the Interleaver device, such as the Chinese utility model patent CN203069824U published on July 17, 2013, and the US patents US20020154845, US6694066, and US7173763. What they have in common is that they all use PBS film to achieve polarization Light splitting and combination of light beams, but using PBS film to generate polarized beams not only has a low extinction ratio, but also the splitting ratio is more sensitive to temperature, and the most important thing is that the reliability of the film layer is poor, so that the overall reliability of the Interleaver device is low.

The optical path difference introduction device in the filter unit of Chinese patent CN203069824U uses a combination of a YVO4 crystal and a BBO crystal. complex

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