JPH0926521A - Optical demultiplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical demultiplexer capable of reducing leakage when plural numbers of signal light beams are demultiplexed and making the respective output ports parallel. SOLUTION: A first dielectric multilayer film filter 13 and a second dielectric multilayer film filter 16 have wavelength selectivity transmitting a wavelength λthrough and reflecting a wavelength λ2 and a signal light beam reflected by the filter 13 is again reflected by the filter 16. When the reflectance (leakage ratio) of the filters 13, 16 for the wavelength λ1 are e.g. 1%, the leakage ratio at the time of being reflected twice by the filters 13, 16 becomes 0.01%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to wavelength division multiplexing (WD).
The present invention relates to an optical demultiplexer that demultiplexes a plurality of signal lights having different wavelengths.

[0002]

2. Description of the Related Art A conventional optical demultiplexer basically multiplexes signal lights of wavelengths λ1 and λ2 input to an input port P1 as shown by a solid line (a structure shown by a broken line will be described later) in FIG. In order to demultiplex the separated light, the dielectric multilayer filter 1 having selectivity for wavelengths λ1 and λ2 transmits the signal light having the wavelength λ1 and outputs the signal light to the output port P2. It is configured to reflect and output to the output port P3.

Here, the dielectric multilayer filter 1 can be constructed to have a high reflectance, and the signal light of the wavelength λ2 is converted into the wavelength λ.
It is easy to set the rate of leaking into the output port P2 on the first side to −30 dB or less. However, it is difficult to set the transmittance of the wavelength λ1 to 100%, and the wavelength λ1 of several%
However, there is a problem that the signal light is reflected and leaks into the output port P3.

Therefore, in the conventional optical demultiplexer, in order to solve the above-mentioned problem of "leakage", as shown by the solid line in FIG. 3, a filter 2 having a wavelength selectivity opposite to that of the filter 1 is filtered. The wavelength λ that is disposed on the reflection optical path side of 1 (the output port P3 side) and leaks into the output port P3 on the wavelength λ2 side.
The signal light of No. 1 is reflected (the signal light of wavelength λ2 is transmitted).

[0005]

However, in the above conventional optical demultiplexer, if the positions and the inclinations of the filters 1 and 2 are deviated, the coupling efficiency between the input port P1 and the output port P3 varies. There is a problem of doing.

Further, in the configuration shown by the solid line in FIGS. 2 and 3, the output ports P2 and P3 are at right angles and are not parallel, so there is the problem that handling is troublesome and the installation area becomes large. In order to solve this problem, as shown by the broken line in FIGS. 2 and 3, a reflection mirror 3 is provided on the wavelength λ2 side to output ports P2 and P3.
Can be made parallel (for example, Japanese Patent Laid-Open No. 3-1
No. 64703), the problem of "leakage" cannot be solved.

The present invention has been made in view of the circumstances of the prior art as described above, and an object thereof is to reduce leakage when demultiplexing a plurality of signal lights and to reduce the output ports. It is to provide an optical demultiplexer that can be parallelized.

[0008]

In order to achieve the above object, the present invention provides a first dielectric multilayer film having a demultiplexing characteristic of transmitting one of two signal lights having different wavelengths and reflecting the other. A filter, having a demultiplexing characteristic similar to that of the first filter, transmitting the one signal light reflected by the first filter, and transmitting the other signal light of the first filter. And a second dielectric multilayer filter that reflects parallel to the direction.

Further, the first and second filters are mounted on the filter substrate so that the transmission direction of the first filter and the reflection direction of the second filter are parallel to each other.

[0010]

In the present invention, since the signal light is reflected twice by the two dielectric multilayer filters having the same demultiplexing characteristic, the leak rate by the filter can be reduced to one half of the square. Therefore, leakage when demultiplexing a plurality of signal lights can be reduced. Moreover, since the transmission direction of the first filter and the reflection direction of the second filter are parallel, each output port can be parallel.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an optical demultiplexer according to an embodiment of the present invention. In FIG. 1, signal lights of wavelengths λ1 and λ2 that are wavelength division multiplexed (WDM) are input via an optical fiber 11. , Is collimated by the collimator lens 12 attached to the end face of the optical fiber 11, and enters the first dielectric multilayer filter 13. The filter 13 has wavelength selectivity of transmitting the wavelength λ1 and reflecting the wavelength λ2, and the signal light of the wavelength λ1 transmitted through the filter 13 is collimated by the collimator lens 14 attached to the end face of the fiber 15 and then collimated. It is output via the fiber 15.

On the other hand, the signal light having the wavelength λ2 reflected by the filter 13 is incident on the second dielectric multilayer filter 16 having the same characteristics as the filter 13, and the wavelength further reflected by the filter 16. Collimator lens 1 in which signal light of λ2 is attached to the end face of fiber 18
After being collimated by 7, it is output via a fiber 18.

The filters 13 and 16 are fixed to the filter substrate 19 so that the incident angle and the reflection angle are 30 °, and the filter substrate 19 is fixed to the base 20.
The base 20 has openings for fitting the optical fibers 11, 15 and 18 so that the incident angle and the reflection angle with respect to the filters 13 and 16 are 30 °, that is, the output optical paths are parallel to each other. There is.

In such a structure, the filter 13,
Assuming that the reflectance (leakage rate) of 16 with respect to the wavelength λ1 is 1% (= 0.01), the leakage rate when reflected twice by the filters 13 and 16 is 0.01% (=
0.0001), and therefore leakage can be reduced and each output port can be parallelized. Further, since the light is reflected twice by the filters 13 and 16, even if the mounting angles of the filter substrate 19 and the base 20 deviate from each other, the filter substrate 19 does not operate on the principle of the double mirror.
It is possible to prevent angular deviation between the incident angle and the outgoing angle.

Further, in the configuration shown in FIG. 1, the optical fibers 11, 15, 18 with the collimator lenses 12, 14, 17 and the filter substrate 19 with the filters 13, 16 are simply fitted to the base 20. Since it can be incorporated with high precision, the cost can be reduced.

[0016]

As described above, according to the present invention,
A first dielectric multilayer filter having a demultiplexing characteristic of transmitting one of two signal lights having different wavelengths and reflecting the other;
It has a demultiplexing characteristic similar to that of the first filter,
A second dielectric multilayer filter that transmits the one signal light reflected by the first filter and reflects the other signal light in parallel to the transmission direction of the first filter. The signal light is reflected twice by the two dielectric multi-layer film filters having the demultiplexing characteristic, so that the leak rate by the filter can be reduced to 1 / square, and thus the plurality of signal lights are demultiplexed. In this case, leakage can be reduced. Moreover, since the transmission direction of the first filter and the reflection direction of the second filter are parallel, each output port can be parallel.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical demultiplexer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional optical demultiplexer.

FIG. 3 is a configuration diagram showing another conventional optical demultiplexer.

[Explanation of symbols]

 13, 16 Dielectric multilayer filter 19 Filter substrate 20 Base

Claims (2)

[Claims] 1. A first dielectric multilayer filter having a demultiplexing characteristic of transmitting one of two signal lights having different wavelengths and reflecting the other, and a demultiplexing characteristic similar to that of the first filter. Having the first
A second dielectric multilayer film filter that transmits the one signal light reflected by the filter and reflects the other signal light in parallel to the transmission direction of the first filter. Optical demultiplexer. 2. The first and second filters are mounted on a filter substrate such that the transmission direction of the first filter and the reflection direction of the second filter are parallel to each other. 1. The optical demultiplexer according to 1.