JPH11352347A - Waveguide type branching/coupling unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to save an excess optical part by forming an element branching/coupling device of the first step as a two-input/2-output branching/coupling device and forming all of the element branching/coupling devices of the second and subsequent steps as one-input/two-output branching/ coupling devices. SOLUTION: The element branching/coupling device D1 of the first step is a two-input/two-output directional coupler. The input ports of Y-branch waveguides are respectively cascade-connected to the output ports of the directional coupler D1 to form the group D2 of the element branching/coupling device of the second step having the four output ports. The respective input ports of the Y-branch waveguides are respectively cascade-connected to the output ports of the respective Y-branch waveguides of the group D2 to form the group D3 of the element branching/coupling device of the third step having the 8 output ports. The input ports of the Y-branch waveguides are likewise cascade connected to the respective output ports of the respective Y-branch waveguides of the group D3 to form the group D4 of the element branching/coupling device of the fourth step having the 16 output ports. The one-input/two-output element branching/coupling devices are thus connected in n-1 steps as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveguide-type branch coupler effective for use in an optical fiber communication system and an optical sensor system.

[0002]

2. Description of the Related Art In an optical fiber communication system as shown in FIG. 3, a signal from one master station 1 has one input and one input.
In the waveguide type branching coupler 2 of the N outputs are divided into N signals, fiber line 3 ₁ of each signal is the _N, 3 _2, ...
3 _N are distributed to _N slave stations 4 _1, 4 _2, ... 4 _N.

An example of the branch coupler 2 used in such a system will be described with reference to FIGS. 4 to 9 for a case of 1 input and 16 outputs, for example. Type branch coupler A in FIG. 4, the Y-branch waveguide I shown in FIG. 5, their input ports I _a and the output port I _b, in tournament over 4 stages each I _c They are cascaded.

[0004] type of branching and coupling device B in FIG. 6, a directional coupler II binding portion II _d are formed as shown in FIG. 7, their input ports II _a and the output port II _b, II
_c are cascade-connected in four stages.
Type branch coupler C of FIG. 8, a directional coupler III binding portion IIId as shown in FIG. 9 are formed, their respective input ports III _a and the output port III _b, III _c Are connected in cascade over four stages.

[0005]

[SUMMARY OF THE INVENTION Incidentally, in an optical communication system shown in FIG. 3, the optical fiber line 3 ₁ while communications between the master station and the slave _station, 3 _2, when monitoring ...... 3 _N An optical line of light having a wavelength λ ₂ different from the communication wavelength λ ₁ as shown in FIG. 10 is provided at a location indicated by an arrow between the master station 1 and the one-input / N-output branch coupler 2. It is necessary to connect a monitoring device (for example, an OTDR) 5 via an optical multiplexer / demultiplexer 6 for multiplexing / demultiplexing light of wavelengths λ ₁ and λ ₂ .

That is, one input and two inputs of the above-described conventional structure.
When the output branching coupler 2 is used, when the optical line monitoring device 5 is connected, an optical multiplexer / demultiplexer (when λ ₁ ≠ λ ₂ ) or an optical coupler (when λ ₁ = λ ₂ ) is used. Requires other light parts. An object of the present invention is to provide a waveguide-type branch coupler capable of monitoring an optical line without requiring the above-mentioned optical components.

[0007]

In order to achieve the above object, according to the present invention, there is provided a waveguide in which an input port of another element branch coupler is cascaded to an output port of each element branch coupler. In the type branch coupler, the first-stage element branch coupler is a two-input / two-output branch coupler, and the first-stage element branch coupler has at least two lights having different wavelengths input to two input ports. And a two-input / two-output branch coupler having no wavelength dependency with respect to the at least two wavelengths to be used, and each of the second and subsequent element branch couplers is a one-input / two-output branch coupler. There is provided a waveguide-type branch coupler.

In the branch coupler according to the present invention, the first-stage element branch coupler is a two-input / two-output branch coupler having no wavelength dependency for at least two wavelengths to be used.
For example, light used for monitoring an optical line can be input to at least one of the input ports.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Explanation will be given based on the plane. FIG. 1 shows two inputs and 16 outputs of the present invention.
It is the schematic which shows a force branching coupler. This branch coupler D
Here, the first-stage element branch coupler D₁Is shown in FIG.
This is a two-input / two-output directional coupler. And
This directional coupler D₁Output port d_Two, D_FourThe figure
Input port I of Y branch waveguide I indicated by 5_aIs each
Second stage element cascaded with four output ports
Branch coupler group D_TwoAnd further form group D_TwoEach Y branch guide
Each output port I of the waveguide_b, I_cY-branch waveguide
I input port I_aAre connected in cascade and eight output ports
D of the third-stage element branching coupler having_ThreeIs formed,
Group D_ThreeOutput port I of each Y-branch waveguide _b,
I_cInput port I of the Y-branch waveguide I_aIs cascaded
Fourth-stage element branch with 16 output ports
Coupler group D_FourAre formed.

[0010] Thus, it is successively cascaded in further embodiments described above the Y-branch waveguide to the group D _4, if a total of n-1 stages connected one input and two-output element branching coupler obtained The branch coupler is a two-input / 2 ^n- output branch coupler.
The element branch couplers connected in cascade in the second and subsequent stages are not limited to the Y-branch optical waveguide I as shown in FIG. 5, but may be the type II shown in FIG. 7 or the type shown in FIG.
III, or a combination of these types I, II, and III as appropriate. Furthermore, by placing a directional coupler D ₁ of the the above 2-input 2-output shown in FIG. 2 in the second and subsequent stages, an input port d _1, d ₂
One only (eg, d ₁₎ of the connected to the output port of the preceding element branching coupler, the other input port d ₂ may be configured not to use among the.

In the directional coupler D ₁ used in the first stage, a signal of wavelength λ ₁ is inputted from its input port d ₁ , and light for monitoring the optical line of wavelength λ ₂ is inputted from the remaining input port d _2. Is entered. As the directional coupler D _1, the branch coupling ratio is wavelength-independent in light between the communication wavelength lambda ₁ of the monitoring wavelength lambda _2, i.e. using a branching coupler is flat wavelength. As such a branch coupler, for example, Topi
cal Meeting on IntegratedPhotonic Research 199
0, W17, an asymmetric Mach-Zehnder interferometer (WINC).

In the directional coupler D ₁ , one input port (d ₁ ) is provided with a filter that passes through the communication wavelength λ ₁ and reflects the monitoring wavelength λ _{2 at} the same time. _Second , it is preferable to dispose a filter that reflects the communication wavelength λ ₁ and passes the monitoring wavelength λ ₂ through, for example, a slit cut in the waveguide. Incidentally, although the optical signal of the wavelength lambda ₂ and the light for optical line monitoring in the above embodiment, the optical signal of the wavelength lambda ₂ is not limited for optical line monitoring, and in light of different wavelengths wavelengths lambda ₁ As long as it is sufficient, light used for other purposes may be used.

[0013]

As is apparent from the above description, the waveguide-type branch coupler of the present invention is formed by cascading the output port of each element branch coupler to the input port of another element branch coupler. In the waveguide type branch coupler, the first-stage element branch coupler is a two-input / two-output branch coupler, and the first-stage element branch coupler has at least two lights having different wavelengths in two input ports. It is a two-input / two-output branch coupler that is input and has no wavelength dependence for at least two operating wavelengths, and all of the second and subsequent element branch couplers are one-input / two-output branch couplers. Since the number of element branch couplers used is the same as that of the conventional branch coupler, the first-stage element branch coupler has a wavelength dependence for at least two used wavelengths. Since there are no two inputs and two outputs, for example, Without even can use them for one as for optical line monitoring can save one extra optical components.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a two-input / 16-output waveguide type branch coupler of the present invention.

FIG. 2 is a schematic diagram of a two-input / two-output directional coupler arranged in a first stage.

FIG. 3 is a schematic diagram showing an optical fiber communication system.

FIG. 4 is a schematic view showing an example of a conventional waveguide type branch coupler.

FIG. 5 is a schematic diagram showing a Y-branch waveguide type element branch coupler used in the branch coupler of FIG. 4;

FIG. 6 is a schematic diagram showing another example of a conventional waveguide-type branch coupler.

FIG. 7 is a schematic diagram of a directional coupler used as an element branch coupler in the branch coupler of FIG. 6;

FIG. 8 is a schematic view showing another example of a conventional waveguide type branch coupler.

FIG. 9 is a schematic diagram showing a directional coupler used as an element branch coupler in the branch coupler of FIG. 8;

FIG. 10 is a schematic diagram of a system interposed for monitoring an optical line in the communication system of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Master station 2 Waveguide type branching coupler 3 _1, 3 _2, ... 3 _N optical fiber line 4 _1, 4, _2, ... 4 _N slave station 5 Optical line monitoring device 6 Optical multiplexer / demultiplexer A, B, C Conventional 1-input / 16-output branch coupler D 2-input / 16-output branch coupler of the present invention I-element branch coupler (Y-branch waveguide) II-element branch coupler (1-input / 2-output directional coupler) III-element branch coupler (1 input and 2 output directional _{coupler) I a, II a, III} a, d 1, d 3 input ports _{I b, I c, II b} , II c, III b, III c, d 2, d ₄ output port

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Isao Oyama 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd.

Claims (1)

[Claims] 1. A waveguide type branch coupler comprising an output port of each element branch coupler connected in cascade to an input port of another element branch coupler, wherein the first-stage element branch coupler has two inputs. A two-output branch coupler, wherein at least two lights having different wavelengths are input to two input ports of the first-stage element branch coupler, and two inputs having no wavelength dependency with respect to the at least two use wavelengths are provided. -A waveguide type branch coupler characterized in that it is a two-output branch coupler, and each of the second and subsequent element branch couplers is a one-input two-output branch coupler.