JP3391650B2 - Optical splitter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical splitter effective for wavelength division multiplex communication and an optical line test system.

[0002]

2. Description of the Related Art With the diversification of needs for communication services, economical and highly functional networks have been demanded.
Optical fiber is installed in each home and cable TV (CAT
V) and other video distribution services and systems for simultaneously performing communication services such as telephone and computer data are being developed. "Access systems for communication / video distribution services", NTTR & D, vol.44, p.1163, 1995 reference).

Furthermore, an in-service test using a wavelength different from the image / communication signal light has been developed for the purpose of economical and efficient management and maintenance of the optical fiber network (N. Tomita, et.
al., "Design and performance of a novel automatic f
iber line testing system with OTDR for optical sub
scriber loops, "J. Lightwave Technol., vol.12, p.71
7, 1994).

For these complicated and diverse optical communication services, it is desired to develop economical and high-performance optical components.
As optical components for communication, there are a bulk type in which individual components are connected, a fiber type in which an optical fiber is processed, and a waveguide type constituted by an optical waveguide on a flat substrate.
Waveguide-type optical components, which are compact, highly integrated, and capable of high functionality, are drawing attention.

FIG. 7 shows a waveguide type optical splitter that distributes video signal light in the wavelength band of 1.55 μm and transmits communication light in the wavelength band of 1.3 μm. In this communication system, an economical video distribution service is provided by a passive one-to-many double-star system, and at the same time a high-speed and safe communication service is provided by a one-to-one single-star system. This optical splitter is made on a quartz flat substrate 1 having a thickness of 1 mm by a silica optical waveguide having a core size of 7 μm × 7 μm, a clad film thickness of 60 μm, and a relative refractive index difference between a core and a clad of 0.45%. It enables a video distribution service for eight subscribers in the 1.55 μm band and a two-way communication service for eight subscribers in the wavelength 1.3 μm band.

Since the silica-based optical waveguide is manufactured by using the same component material as that of the optical fiber and utilizing the advanced semiconductor processing technology, it is intended to provide an optical component having high functionality, low loss and excellent stability. In recent years, it is an optical waveguide that has received a great deal of attention (for example, M. Kawachi, "Recent progress in silica-bas
ed planar lightwave circuits on silicon, "IEE Pro
c.- Optoelectron., vol.143, p.257, 1996).

In this optical splitter, as shown in FIG. 7, a branch circuit 2 in which three Y branches 21 are connected in three stages is formed in a first input waveguide 31, and its output port passes through a wavelength multiplexer / demultiplexer 41. It is connected to the output waveguide 33. Four second input waveguides 3 are provided on each side of the first input waveguide 31.
2 is arranged, and the output waveguide 3 is provided via the wavelength multiplexer / demultiplexer 41.
It is connected to 3. The video signal light in the wavelength band of 1.55 μm is incident from the first input waveguide 31 and is transmitted by the branch circuit 2 to 8
The divided signal light is divided into two and passes through the wavelength multiplexer / demultiplexer 41 to reach the output waveguide 33. On the other hand, the 1.3 μm wavelength band communication light from the station to the subscriber side enters from the second input waveguide 32 and is guided to the output waveguide 33 via the wavelength multiplexer / demultiplexer 41. It should be noted that the 1.3 μm band communication light from the subscriber side to the station passes through the reverse path, propagates through the transmission path, and then the output waveguide 3
3. It is guided to the second input waveguide 32 via the wavelength multiplexer / demultiplexer 41.

The wavelength multiplexer / demultiplexer 41 of the embodiment is composed of a Mach-Zehnder optical interferometer in which two directional couplers 71, 71 are connected, as shown in FIG. Since this Mach-Zehnder optical interferometer is easy to design and manufacture, it is widely used as an effective circuit for a waveguide-type wavelength multiplexer / demultiplexer (Kominato et al., "Mach-Zehnder". Waveguide type optical WDM circuit composed of interferometer ", IEICE Transactions CI, vol.J73-CI, p.354, 1990).

In this embodiment of the optical splitter, as shown in FIG. 7, an input / output fiber is connected to the end face of the waveguide.
A first input fiber 51 is connected to the first input waveguide 31, and a second input fiber 52 is connected to the second input waveguide 32. These input optical fibers are arranged and fixed on the fiber holding member 61 at an interval equal to the arrangement interval of the input waveguides. Since the second input fiber 52 is multicore, a multicore tape fiber 54 in which they are bundled is usually used. Further, the output fiber 53 is end-connected to the output waveguide 33. The output fiber 53 is also arranged and fixed to the fiber holding member 62 at an interval equal to the array interval of each output waveguide. Since the output fiber 53 is also multicore, a multicore tape fiber 55 which is a bundle of them is usually used.

As another application of the optical splitter having the same structure in which a branch circuit and a Mach-Zehnder optical interferometer are combined, 1.3 μm band bidirectional communication and 1.55 μm band video distribution are provided by a passive double star system. And 1.65 μm
A system for conducting line tests in the band has been proposed (F. Yam
amoto, et al., "In-service remote access and measu
rement method for passive double star networks, "5
th Conference on Optical / Hybrid Access Networks,
See Montreal, Canada, 5.02, 1993). In this case, the Mach-Zehnder optical interferometer is designed to function as a wavelength independent coupler.

That is, the image signal light in the 1.55 μm band is the first
The light enters from the input waveguide 31, is branched into eight by the branch circuit, and then reaches the output waveguide 33 through the optical coupler 41. On the other hand, the 1.3 μm band communication light from the subscriber side is 1.
It reaches the first input waveguide 31 by following a path opposite to that of the video signal light of the 55 μm band. The test light of 1.65 μm is introduced from the second input waveguide side, and is output by the optical coupler to the output waveguide 3
After coupling to 3, the optical fiber is sent to the transmission line fiber and various tests are executed. Examples of the test include an OTDR test in which backscattered light is monitored to detect a break point.

[0012]

In the conventional optical splitter shown in FIG. 7, the second input waveguide 32 is arranged on the side opposite to the output waveguide 33 due to the structure of the waveguide type Mach-Zehnder optical interferometer. . Therefore, the second input waveguide 32 always crosses the waveguide of the branch circuit 2 at once at the X intersection 22 except for the two waveguides at both ends. At the intersection of the two waveguides, the propagating light leaks between the waveguides, causing deterioration of the video signal and crosstalk during communication. It is known that the smaller the crossing angle, the larger the crosstalk amount and the excess loss. For example, a cross angle of 13 degrees or more is required to suppress the crosstalk amount to -30 dB or less, and the excess loss at this time is about 0.1 dB.

On the other hand, a curved waveguide is required for the layout of the branch circuit 2 and the second input waveguide 32, and this curved portion has a certain radius of curvature (see FIG. 7) in order to suppress excessive loss. It must be bent by 15 mm in the conventional example). Due to the conditions of the minimum intersection angle and the minimum radius of curvature, the layout of the optical splitter is limited, and as a result, there is a problem that the circuit design takes time and effort.

In particular, as the number of branches increases, circuit design becomes more complicated and difficult. At the same time, the effect of an increase in loss due to an increase in the number of intersections becomes significant. The image distribution signal light propagating at both ends of the output waveguide branched from the first input waveguide by N branches is (N
/ 2-1) X crossing portions are passed, so in a 32-branching optical splitter, excess crossing loss is about 1.5 dB.

Further, since the branching ratio of the Y branch 21 is easily influenced by the state of the waveguide mode before branching, the waveguide mode is disturbed by the crossing of the waveguides in the branch circuit 2 and, as a result, the video signal light. There was a risk of variations in the branching ratio and fluctuations in the signal light power.

Further, there is a problem in that the Mach-Zehnder optical interferometer and the branch circuit are combined. When the branch circuit and the wavelength multiplexer / demultiplexer are manufactured by the optical waveguides on the same substrate as in the conventional example, the optimum conditions for manufacturing the Y branch and the directional coupler constituting each are strictly different. Therefore, in order to combine these two types of circuits, it was necessary to fabricate them under intermediate conditions deviated from the respective optimum conditions. For this reason, the characteristics of each circuit cannot be sufficiently obtained, and as a result, the characteristics of the optical splitter are varied, which is one of the factors that lower the yield.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical splitter that facilitates circuit design and improves circuit characteristics and productivity.

[0018]

An optical splitter of the present invention which achieves such an object comprises one or a plurality of first input waveguides formed by an optical waveguide on a substrate, a branch circuit, and a plurality of branch circuits. A first optical circuit consisting of a book output waveguide;
A plurality of second optical circuits each of which is formed by an optical waveguide on a substrate, and one second input waveguide corresponds to only one output waveguide; An optical splitter in which an output waveguide of a second optical circuit is shared, wherein a wavelength filter that separates signal light by transmission and reflection is inserted into the output waveguide and is incident from the second input waveguide. The reflected light is reflected by the wavelength filter and coupled to the output waveguide, and the second input waveguide is arranged on the side opposite to the branch circuit with respect to the wavelength filter, and in the second optical circuit, The second input waveguide and the output waveguide have an intersection intersecting at 15 °, and the wavelength filter is formed near the center of the intersection at a right angle to the bisector having an intersection angle of 15 °. The second input waveguide and the output waveguide are inserted into the groove. The path is guided to the same substrate end face while being bent so as not to intersect the adjacent two optical circuits, and the second input waveguide and the output waveguide are alternately arranged at 127 μm intervals on the substrate end face. It is, and the second
In the vicinity of the wavelength filter of the second optical circuit,
The pair of second input conductors forming a second optical circuit.
The maximum distance between the waveguide and the one output waveguide is
The maximum value of the interval becomes larger than the 127 μm interval.
So that the second input waveguide and the output waveguide are bent.
It is characterized in that is.

[0019]

Furthermore, these said optical splitters are
The wavelength filter filters the signal light in the first wavelength band by about 10
It can be characterized by transmitting 0% and reflecting almost 100% of the signal light in the second wavelength band.

Further, the wavelength filter can be characterized in that it separates the signal light in a required wavelength range at a substantially constant rate.

Further, it can be characterized in that the wavelength filter separates the signal light in the first wavelength band at a substantially constant rate and reflects the signal light in the second wavelength band by almost 100%.

In the present invention, since the light path is changed in the opposite direction by the reflection function of the wavelength filter, the waveguides for guiding the input / output light can be arranged on the same waveguide end face. That is, the second input waveguide arranged on the input side by the conventional optical splitter can be arranged on the output side, and as a result, the second input waveguide can be arranged without intersecting the waveguide of the branch circuit of the second input waveguide.

Therefore, since the circuit layout is not limited by the minimum crossing angle as in the conventional case, the design becomes easier and the labor and time are less required than in the conventional case. Also, problems such as crosstalk due to crossing, excessive loss, and branching ratio variation can be avoided. These are particularly effective when the number of branches is large.

Further, since the wavelength multiplexer / demultiplexer and the branch circuit are separately manufactured, they can be manufactured under the optimum conditions for each, and as a result, the function of the entire optical splitter circuit can be improved.

Further, since the common optical splitter waveguide circuit can be used for the wavelength filters having various filter functions, the layout of the optical splitter circuit can be changed in accordance with the change or diversification of the multiplexing / demultiplexing specifications of the communication system. You can flexibly respond without changing.

As described above, the optical splitter of the present invention is
In addition to each function obtained by combining an optical branch circuit and a wavelength filter, it solves various problems of circuit layout and characteristic deterioration due to waveguide crossing, which are possessed by an optical splitter with a conventional composite circuit configuration. It is possible to promote the improvement of characteristics.

The optical splitter of the present invention summarizes the concepts of both an optical splitter having only waveguide chips without optical fibers provided at both ends and an optical splitter module having optical fibers provided at both ends of the optical splitter. To do.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIGS. 1 and 2 show a first embodiment of the present invention in which a video signal light having a wavelength of 1.55 μm is distributed and a communication light is transmitted in a wavelength of 1.3 μm. 8
It is a figure explaining a branch light splitter, and is a top view and a side view, respectively.

Since the substrate 1 and the branching structure of this optical splitter are the same as those of the conventional example shown in FIG. 7, the same members are designated by the same reference numerals and will be described below. 1 and 2, reference numeral 1 is a substrate, 2 is a branch circuit, 21 is a Y branch, and 3
1 is a first input waveguide, 32 is a second input waveguide, 33 is an output waveguide, 42 is a wavelength filter, 43 is an insertion groove, 5 is a fiber array, 51 is a first input fiber, and 52 is a second input fiber. , 53 are output fibers, 54 and 55 are multi-core tape fibers, and 61 and 62 are fiber holding members.

As shown in FIGS. 1 and 2, the branch circuit 2 in which three Y-branches 21 are connected in series is formed in the first input waveguide 31, and the output waveguide 33 is slanted so as to cross it. The insertion groove 43 is formed, and the wavelength filter 42 is inserted into the insertion groove 43.

As shown in FIG. 3, the wavelength filter 42 transmits almost 100% of light in the first wavelength band of 1.55 μm, and transmits light in the second wavelength band of 1.3 μm. It is manufactured so as to reflect almost 100% of light. Such a wavelength filter is manufactured by using SiO ₂ on a polyimide thin film.
A dielectric multilayer filter in which TiO ₂ and TiO ₂ are deposited alternately can be produced by a known technique (T. Oguchi et al. "Diel
ectric multi-layered interference filters deposited
on polyimide films. "Electron. Lett. vol.27, p.39
1, 1991).

Since the wavelength filter composed of such a normal dielectric multi-layered film utilizes a wider variety of interference effects than the waveguide type Mach-Zehnder optical interferometer, it is possible to realize highly functional and multifunctional filter characteristics. . Therefore, the multiplexing / demultiplexing characteristic can be improved as compared with the conventional case.

In this embodiment, the insertion groove 43 has a width of 3
It is manufactured with a normal dicing saw at a depth of 0 μm and a depth of 200 μm. In this, the wavelength filter 42 having a width of about 20 μm
However, the present invention is not limited to this.

FIG. 4 is an enlarged view of a wavelength multiplexer / demultiplexer using this wavelength filter 42. The second input waveguide 32 and the output waveguide 33 are intersected with each other, and the charging groove 43 is formed in the vicinity of the center of the intersection at a right angle (direction orthogonal to) the bisector of the intersection angle. The wavelength filter 42 is inserted in 43. As a result, the second input waveguide 32 and the output waveguide 3
Since the 1.3 μm signal light propagating through 3 and 3 is reflected and coupled by the wavelength filter 42, the second input waveguide 32 is arranged on the side opposite to the branch circuit side and does not intersect with the waveguide of the branch circuit. Therefore, the layout of the branch circuit can be designed by itself, and the problem due to the intersection can be avoided. The crossing angle α between the second input waveguide 32 and the output waveguide 33 is 50 dB for the return loss from the wavelength filter 42 and the fixing adhesive 44.
It was set to 15 degrees to make it above.

The mounting form of this optical splitter is shown in FIGS.
As shown in (1), an input / output fiber is connected to the end face of the waveguide. The first input fiber 5 is connected to the first input waveguide 31.
1 is end-face connected. The first input fiber 51 is fixed by a fiber holding member 61, and is connected and fixed together with the end surface of the quartz substrate 1 by an ultraviolet curable resin. A fiber array 5 having the same number of fibers as the number of waveguides is end-connected to the second input waveguide 32 and the output waveguide 33. In the fiber array 5, the second input fibers 52 and the output fibers 53 are alternately arranged and fixed by the fiber holding member 62 at an interval equal to the array interval of the input / output waveguides, and the second input waveguides 42 and The end face is connected to the output waveguide 43.

Second input fiber 52 and output fiber 53
Since each of them has a multi-core structure, usually, multi-core tape fibers 54 and 55 that are a bundle of them are used and aggregated for each type.
The multi-core tape fibers 54 and 55 are shifted and overlapped by about one fiber, and the fibers separated from the multi-core tape fiber into a single fiber are respectively the second input fiber 52 and the output fiber 5.
3, and these are alternately arranged in a horizontal row for each type to form the fiber array 5. The fiber spacing was 127 μm, which was slightly larger than the fiber outer diameter of 125 μm, and the spacing between the second input waveguides 32 and the output waveguides 33 arranged alternately was also 127 μm.

[Second Embodiment] Next, a second embodiment of the present invention will be described. The second embodiment of the optical splitter of the present invention is based on the 1.3 μm band bidirectional communication and 1.55
Provide μm band video distribution by passive double star system,
It is used in a system that performs an optical line test in the 1.65 μm band.

For this purpose, the same waveguide chip as in Embodiment 1 can be used, and only the wavelength filter needs to be changed to one suitable for this application. As shown in FIG. 5, the wavelength filter for this system has a transmittance of about 80% in the wavelength range of 1.2 to 1.7 μm,
Therefore, the reflectance is about 20%. Such a wavelength filter can be easily manufactured by adjusting the thickness and the like of the dielectric multilayer film that constitutes the wavelength filter.

Therefore, the wavelength filter in FIG.
If it is replaced with a bidirectional signal of 1.3 μm between the first input fiber 51 and the output fiber 53 and 1.55 μm
A band image signal can be input and output, and test light of 1.65 μm can be input from the second input fiber 52 side and output to the output fiber 53. At this time, since the transmittance of the wavelength filter is about 80%, the signal light (1.3 μm, 1.5
5 μm) has a loss of about 1 dB when passing through the wavelength filter, and the test light has a loss of about 7 dB when reflected by the wavelength filter because the reflectance of the wavelength filter is about 20%.

These losses are in principle generated when the branching and coupling phenomenon of light is generated, and are also generated in the conventional waveguide type Mach-Zehnder optical interferometer. Even in the wavelength range other than the test light, which is 1.3 to 1.55 μm, about 20% is reflected at the time of laying the fiber.
This is because light having a wavelength of 1.55 μm may be used as the test light.

[Third Embodiment] Next, a third embodiment of the present invention will be described. The third embodiment of the optical splitter of the present invention is the same as the second embodiment except that the characteristics of the wavelength filter are changed to those shown in FIG. This wavelength filter has wavelengths 1.3 and 1.
About 80% of the signal light is transmitted in the 55 μm band (about 20% is reflected), and almost 1 in the second wavelength band of 1.65 μm.
It reflects the signal light of 00%.

Such wavelength characteristics are difficult to realize with a waveguide type Mach-Zehnder interferometer, but can be realized by using a dielectric multilayer film wavelength filter utilizing the multiple interference effect. With this wavelength filter, all the test light in the wavelength range of 1.65 μm is reflected, and compared with the case of the second embodiment,
It can be greatly reduced. For example, in an OTDR test in which backscattered light is monitored to detect a break point, the loss of test light can be reduced by about 14 dB in a round trip.

In the above embodiment, one first
Although an example in which the input waveguide and the second input waveguide of eight are branched into eight output waveguides has been described, the number of input / output ports of the optical splitter of the present invention is not limited to these.

Although an example in which a Y branch is used as the branch circuit is shown, other branch coupling circuits such as a directional coupler, a Mach-Zehnder optical interferometer, an MMI (Multi-Mode I) are used.
(nterference) coupler, a star coupler by slab coupling, or a circuit combining a plurality of these.

In particular, the number of the first input waveguides is changed to two, and the Y branch of the first stage (the leftmost end of the figure) of FIG. 1 is replaced with a two-input, two-output guided-wavelength independent 50% coupler. The one in which the signal light of each of the two first input waveguides is split into two is a communication in which one of the first input waveguides is used as a backup port to double the line and improve reliability. An optical splitter compatible with the system can be configured.

Further, the optical waveguide material constituting the optical splitter of the present invention is not limited to silica glass, and other multi-component glass, dielectric crystals such as lithium niobate waveguide, acrylic, silicone, polyimide, etc. Organic polymers and semiconductor materials such as silicon and gallium arsenide are also included.

Further, the optical splitter according to the present invention has a structure of 1.2-
The band is not limited to the band of 1.7 μm. For example,
The splitter can be applied to communication using a 0.8 μm band or 0.6 μm band laser beam, a sensor, optical interconnection, and the like.

[0050]

As described above, according to the present invention, a wavelength filter having a reflection function is inserted in the output waveguide of the optical branching circuit for distributing the signal light from the first input waveguide, and the output is provided. The second component is arranged so that the signal light incident from the same end face as the waveguide end is reflected by the wavelength filter and is coupled to the output waveguide.
By providing the input waveguide, the intersection between the second input waveguide and the optical branch circuit is eliminated, and the circuit design is facilitated, and problems such as crosstalk, excessive loss, and branching ratio variation due to the intersection can be avoided, and the characteristics are improved. It can be expected to improve productivity.

Further, since the wavelength filter which is usually composed of the dielectric multilayer film can realize various filter characteristics by utilizing the multiple interference effect, the optical splitter of this structure is flexible to the diversification of the communication system. Can respond.

[Brief description of drawings]

FIG. 1 is a plan view illustrating a configuration of an 8-branching optical splitter for 1.55 μm band image distribution and 1.3 μm band communication as a first embodiment of an optical splitter of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a diagram for explaining the characteristics of the wavelength filter that constitutes the optical splitter of the present invention, in which almost 100% of the light in the 1.55 μm wavelength band that constitutes the first embodiment is transmitted and the wavelength of 1.3
The wavelength filter reflects almost 100% of light in the μm band.

FIG. 4 is a wavelength filter that constitutes the optical splitter according to the first embodiment.

FIG. 5 is a wavelength of 1.2 to 1.7 μ constituting the second embodiment.
It is a filter that transmits about 80% of the signal light and reflects about 20% of the signal light in the range of m.

FIGS. 6A and 6B are wavelengths 1.3 and 1.55 constituting the third embodiment.
This is the wavelength characteristic of the filter that transmits about 80% of the signal light in the μm band (reflects about 20%) and reflects almost 100% of the signal light in the wavelength 1.65 μm band.

FIG. 7 is a plan view illustrating a configuration of a conventional optical splitter.

FIG. 8 is an enlarged view for explaining the configuration and function of the wavelength multiplexer / demultiplexer, which is a guided-wave Mach-Zehnder optical interferometer used in a conventional optical splitter.

[Explanation of symbols]

1 substrate 2 branch circuits 21 Y branch 22 X cross 31 First Input Waveguide 32 Second Input Waveguide 33 Output waveguide 41 wavelength multiplexer / demultiplexer 42 wavelength filter 43 insertion groove 44 UV curable adhesive 5 Fiber array 51 First Input Fiber 52 Second input fiber 53 Output fiber 54,55 Multi-core tape fiber 61,62 Fiber holding member

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Fumiaki Hanawa 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Takao Fukumitsu 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nihon Telegraph and Telephone Corporation (72) Inventor Makoto Sumita 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) Reference JP-A-1-144003 (JP, A) ) JP-A-8-248266 (JP, A) JP-A-6-18744 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/12 G01J 3/12 G02B 6 / 30

Claims (4)

(57) [Claims] 1. A first optical circuit comprising one or a plurality of first input waveguides formed by an optical waveguide on a substrate, a branch circuit, and a plurality of output waveguides, and a first optical circuit on the substrate. A plurality of second optical circuits, each of which is formed of an optical waveguide and in which one second input waveguide corresponds to only one output waveguide, is provided, and the output waveguide of the first optical circuit and the second optical circuit are provided. An optical splitter in which an output waveguide of an optical circuit is shared, wherein a wavelength filter that separates signal light by transmission and reflection is inserted into the output waveguide, and light incident from the second input waveguide is , Reflected by the wavelength filter and coupled to the output waveguide, the second input waveguide being disposed on the opposite side of the wavelength filter from the branch circuit, in the second optical circuit, the second input Intersection where the waveguide and the output waveguide intersect at 15 ° Portion, the wavelength filter is inserted in a groove formed in the vicinity of the center of the intersecting portion at a right angle to the bisector of the intersecting angle of 15 °, and the second input waveguide and the output waveguide are provided. Is guided to the same substrate end face while being bent so as not to intersect the adjacent second optical circuit, and at the substrate end face, the second input waveguide and the output waveguide are alternately arranged at 127 μm intervals , And in the vicinity of the wavelength filter of the second optical circuit,
The pair of one of the second optical circuits constituting a plurality of second optical circuits
The maximum distance between the second input waveguide and the one output waveguide
Therefore, the maximum value of the interval is greater than the 127 μm interval.
The second input waveguide and the output waveguide so as to be large
An optical splitter characterized in that and are bent . 2. The wavelength filter according to claim 1, wherein almost 100% of the signal light in the first wavelength band is transmitted and 100% of the signal light in the second wavelength band is reflected. Optical splitter. 3. The optical splitter according to claim 1, wherein the wavelength filter separates the signal light in a required wavelength range at a substantially constant rate. 4. The wavelength filter separates the signal light of the first wavelength band at a substantially constant rate and reflects the signal light of the second wavelength band by almost 100%. The described optical splitter.