JP2002023002A - Optical coupling and branching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such an optical coupling and branching device for n wavelength that is lower in cost and more compact in size by using an existing optical system. SOLUTION: The optical coupling and branching device for (n-1) wavelength is constituted of a filter unit in which (n-2) sheets (n is an integer and 4<=n<=9) of a selectively transmitting and reflecting filter (selective filter) (F(k)) [k is an integer of 1 to (n--2)] are combinedly arranged on the reflecting optical axis successively on mutually parallel planes A, B; an external optical input/ output part on the reflecting optical axis of the selective filter F(1) on the outside of the filter unit; and an optical input/output part (P(k)) [k is an integer of 1 to (n-1)] at (n-1) places on the transmitting optical axis of the selective filter F(k) and on the reflecting optical axis of F(n-2). On the optical axis between the external optical input/output part and the selective filter (F(1)), the selective filter is provided, which transmits the light having a wavelength all equivalent to the optical input/output part (P(k)) and which reflects the light having other different wavelength; also, an optical input/output part (P0) is provided on the reflecting optical axis of this filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical demultiplexer / demultiplexer used for multiplexing or demultiplexing a plurality of signal lights having different wavelengths.

[0002]

2. Description of the Related Art An optical demultiplexer / multiplexer having a function of multiplexing a plurality of signal lights having different wavelengths, or demultiplexing a plurality of multiplexed signal lights into respective wavelength components, comprises: Various schemes have been devised, and as one of them, a technique using a selective transmission / reflection filter is known. FIG. 4 is a diagram illustrating an example of a conventional optical demultiplexer / multiplexer using a selective transmission / reflection filter.

[0003]

SUMMARY OF THE INVENTION The present invention relates to an optical multiplexer / demultiplexer that uses a combination of a plurality of selective transmission / reflection filters, thereby suppressing the spread of a light beam by shortening the optical path length as much as possible and improving the performance. The present invention proposes a structure for keeping the size of the entire device as small as possible while holding it.

[0004]

That is, the present invention provides:
Planes A and (n-2) (where n is an integer of 4 ≦ n ≦ 9) selective transmission reflection filters (F (k)) [k is an integer of 1 to (n−2)] are parallel to each other. A filter unit sequentially coupled to the plane B with a reflection optical axis, an external light input / output unit (E (0)) on a reflection optical axis of the selective transmission reflection filter F (1) outside the filter unit, and (N-1) light input / output units (P (k)) on the transmission optical axis of the selective transmission reflection filter F (k) and on the reflection optical axis of F (n-2)
In the optical demultiplexer / multiplexer having the wavelength (n-1) consisting of [k is an integer of 1 to (n-1)], the external optical input / output unit (E0) and the selective transmission reflection filter (F (1) ), And a selective transmission reflection filter (F0) that transmits light of all wavelengths corresponding to the light input / output unit (P (k)) and reflects light of different wavelengths. This is an n-wavelength optical demultiplexer / multiplexer provided with an optical input / output unit (P0) on the reflected optical axis.

As the selective transmission / reflection filter in the present invention, a known dielectric multilayer filter is suitable. Dielectric multilayer filters are manufactured, for example, by alternately stacking dozens of low-refractive-index thin films (such as silicon oxide) and high-refractive-index thin films (such as titanium oxide), and precisely stacking these films. By controlling, a desired short wavelength band pass filter (SPF), long wavelength band pass filter (LPF),
Or it is possible to obtain a band pass filter (BPF). The dielectric multilayer filter filters light in the reflection area by approximately one.
It is very suitable in that it reflects 00% and has a transmittance close to 100% for the transmission region. In addition, as a material of the filter unit, metal, ceramics, plastic, or the like can be used, and preferable examples of the material include brass, stainless steel, machineable ceramics, and epoxy resin. These use the inside part through which light passes as a cavity. In addition, when a transparent material such as quartz glass is used in the wavelength range to be used, it is also possible to use the material only for the outer shape processing while keeping the inside as it is.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical demultiplexer / multiplexer according to the present invention will be described in more detail with reference to embodiments. The following examples are for the purpose of specifically explaining, and do not limit the embodiments and the scope of the present invention. Embodiment 1 FIG. 1 is a plan view of a four-wavelength optical multiplexer / demultiplexer showing an example of the present invention. In FIG. 1, a filter unit (2) made of stainless steel is fixed to a central portion of a housing (1). The filter unit (2) has a flat surface A at its end.
And the plane B are parallel to each other, and the plane A or the plane B is provided with the selective transmission reflection filter (F0, F1, F2).
2) is attached in close contact, and the portion through which light inside the filter unit passes is hollow. The plane A
The plane B is obliquely arranged at an angle of 10 degrees with respect to the side of the housing. On both sides of the filter unit 2, a light input / output unit (P0, P1, P2, P3) and an external light input / output unit (E0) are provided on the transmission optical axis according to the mounting position of the selective transmission / reflection filter. It is fixed to (1).
Although not shown, these optical input / output units are composed of an optical fiber and a collimating lens attached to the tip thereof.

From the external optical input / output unit (E0), four wavelengths (λ1, λ2, λ3, λ4, where λ1 <λ2 <λ3 <
The case where the light multiplexed with λ4) is incident will be described as an example. Each selective transmission reflection filter (F0, F1, F
The characteristic 2) is as shown in FIG. Light incident from the outside is transmitted through a selective transmission reflection filter F0 (S
PF) reflects light of wavelength λ4, and the reflected light reaches the light input / output unit (P0). The light (λ1 + λ2 + λ3) transmitted through the selective transmission / reflection filter F0 is transmitted through the selective transmission / reflection filter F1 (SPF) attached to the plane B, and the transmitted light reaches the light input / output unit (P1). The light (λ2 + λ3) reflected by the selective transmission / reflection filter F1 is transmitted through a selective transmission / reflection filter F2 (SPF) provided on the plane A, and the transmitted light reaches the light input / output unit (P2). The reflected light (λ3) at F2 passes through the plane B and reaches the light input / output unit (P3). Thus, λ1, λ
Light of four wavelengths of 2, λ3 and λ4 is P0 and P1,
The light is split into the optical input / output units P2 and P3, respectively. Also,
When the light travels in the opposite direction, it functions as a multiplexer.

As a specific combination of wavelengths, λ1:
1515 nm, λ2: 1535 nm, λ3: 1555n
m, λ4: 1575 nm, and light of each wavelength was incident from E0 and measured at each port. The maximum insertion loss ≧ ─1.5 dB, isolation ≦ ─2
It was a good result of 0 dB.

A feature of the present invention is that an external optical input / output unit (E0)
Before the light from the filter reaches the selective transmission / reflection filter (F1), the selective transmission / reflection filter (F0) and the light input / output unit (P
0). With this configuration, it is possible to shorten the sum of the optical path lengths with respect to the number of wavelengths to be demultiplexed or multiplexed. As a result, it is possible to minimize the spread of the light beam and obtain good characteristics. Can be. Another advantage is that the width (w) can be minimized by rational layout design, and the device can be made compact.

In the first embodiment, an example is shown as a combination of an SPF (short wavelength bandpass filter), but the same function is provided by an LPF (long wavelength bandpass filter) or a BPF.
(Band-pass filter). In order to split or combine light of n kinds of wavelengths, at least (n-
1) Although one selective transmission / reflection filter is required, the optical input / output unit (P
It is also effective to add a selective transmission / reflection filter before (k)). The upper limit of the number of wavelengths that can be demultiplexed or multiplexed in the configuration of the present invention depends on the characteristics of the selective transmission / reflection filter to be used, the margin of the system, and the like. It is generally considered that the number of wavelengths is about 9 to obtain. The angle of incidence from the external light input / output unit to the plane A of the optical filter unit is not particularly limited, but is preferably 15 degrees or less as an oblique incidence angle from the viewpoint of filter characteristics.

Second Embodiment FIG. 3 is a plan view showing a four-wavelength optical demultiplexer / multiplexer according to a second embodiment. In the present embodiment, a part of the plane A of the filter unit in the first embodiment is obliquely formed at an angle of 10 degrees in the opposite direction to the side of the housing as shown in FIG.
The optical input / output unit (P0) is moved from the external optical input / output unit (E0) to F1.
Are provided on the side opposite to the other light input / output units with respect to the straight line reaching. The mechanism of demultiplexing and multiplexing is the same as in the first embodiment. However, as a problem in the arrangement inside the housing, it is difficult to arrange the optical input / output unit (P0) in the form of the first embodiment. The embodiment of the present invention is effective.

[0012]

As is apparent from the embodiments and the detailed description of the invention, the optical demultiplexer / multiplexer according to the present invention is extremely high-performance and compact, and can be suitably used for a WDM transmission device and the like. .

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of an optical demultiplexer / multiplexer according to the present invention.

FIG. 2 is a diagram illustrating characteristics of a selective transmission reflection filter according to the first embodiment.

FIG. 3 is a plan view showing an example of an optical demultiplexer / multiplexer according to the present invention.

FIG. 4 is a plan view showing an example of a conventional optical demultiplexer / multiplexer.

[Explanation of symbols]

E0: external light input / output unit, F0 to F3: selective transmission / reflection filter, P0 to P4: light input / output unit

Claims (2)

[Claims] (1) (n-2) sheets (where n is 4 ≦ n ≦ 9)
) Selective transmission reflection filter (F (k)) [k is 1
, (Integer of (n−2)) are sequentially coupled on a plane A and a plane B parallel to each other with a reflection optical axis,
The selective transmission reflection filter F outside the filter unit
The external light input / output unit (E (0)) on the reflection optical axis of (1) and the transmission light axis of the selective transmission / reflection filter F (k) and F
(N-1) wavelength consisting of (n-1) light input / output portions (P (k)) [k is an integer of 1 to (n-1)] with respect to the (n-2) reflected optical axis The optical input / output unit (P (k)) is disposed on the optical axis between the external optical input / output unit (E0) and the selective transmission / reflection filter (F (1)). And a light transmitting / reflecting filter (F0) for transmitting light of all wavelengths corresponding to the above, and reflecting light of different wavelengths, and a light component of n wavelengths provided with a light input / output unit (P0) on the reflected optical axis. Wave combiner. 2. The filter unit is composed of a block made of metal, ceramics, or plastic. The block has a portion through which light passes as a space, and a selective transmission / reflection filter F (k) is provided on the surface of the block. The optical demultiplexer / multiplexer according to claim 1, wherein the optical demultiplexer / multiplexer has a fixed structure.