JPS613107A - Optical multiplexer and demultiplexer - Google Patents

Abstract

PURPOSE:To reduce a loss, and also to simplify an assembling work by installing an interference film filter to the end face containing an optical fiber branch point of a glass rod formed as a composite optical waveguide by embedding a branch optical fiber, and combining and coupling plural rods. CONSTITUTION:Rays of light having wavelengths of lambda1 and lambda2 is made incident from an optical fiber 1 of a glass rod 2, and the light of lambda2 and the light of lambda1 are made to demultiplex to a glass rod 3 and a glass rod 4, respectively, by an interference film filter 6. In case of multiplexing said rays, on the contrary, the rays of lambda2 and lambda1 of the respective optical fibers 1 of the glass rod 3 and 4 are made incident, by which the light of both the wavelengths lambda1, lambda2 are multiplexed and emitted from the optical fiber 1 of the glass rod 2. The glass rod 2 and 3 are coupled at an angle theta, hold an angle of theta/2 with the end face of the coupled body, and the glass rod 4 is coupled through the interference film filter 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical multiplexer/demultiplexer for optical communications that has low insertion loss and requires fewer work steps.

[Background of the invention]

Many types of optical multiplexer/demultiplexers have been proposed in the past, but they can be roughly divided into those using angular dispersion elements (prisms, diffraction gratings) and those using interference films. Here, we will discuss the case where an interference film is used together with an optical fiber and a guiding waveguide. A method of polishing the end face of an optical fiber diagonally and adhering an interference film, extracting light with nine different wavelengths as transmitted light and reflected light, and guiding each light to another optical fiber (for example, 58-134617
) is generally known as an optical multiplexer/demultiplexer using optical fibers. The advantage of this method is that the parts can be made smaller, but it requires advanced techniques in processing the end face of the optical fiber, depositing the interference film, and handling it, which poses a problem in terms of mass production. Another method is a method using a leading waveguide (for example, Japanese Patent Application No. 72153/1983). This method alleviates the optical fine-tuning that took a lot of time in conventional optical multiplexer/demultiplexers (e.g., Japanese Patent Applications 57-32037 and 57-32038), and it is economical because the number of work steps is reduced. It is advantageous in terms of However, due to the slow progress in optical waveguide manufacturing technology, waveguide loss and coupling loss between fiber and waveguide are large. In addition, an element with demultiplexing characteristics in the waveguide (
Because the technology for inserting (for example, an interference film filter) is immature, it lacks reliability as an optical circuit component.

[Purpose of the invention]

The present invention provides an economical optical multiplexer/demultiplexer that reduces the coupling loss between the transmission optical fiber and the optical multiplexer/demultiplexer and the loss within the optical multiplexer/demultiplexer, and is easy to work with and automatically assembled. The purpose is to

[Summary of the invention]

In order to achieve the above object, the optical multiplexer/demultiplexer according to the present invention is basically constructed by attaching an interference film filter to the end surface of a glass rod serving as a composite leading wavepath by embedding a branched optical fiber. The optical multiplexer/demultiplexer has low loss and is easy to assemble by combining and connecting a plurality of basic rods.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of the basic principle of an optical multiplexer/demultiplexer according to the present invention, FIG. 2 is a sectional view of the above embodiment, and FIG. 3 is a plan view showing a specific embodiment of the present invention. FIG. 4 is a partial sectional view showing an example of the basic rod constituting the above embodiment. In FIG. 1, the glass rods 2 and 3 in which the optical fibers 1 are embedded are bonded together at the bonding surfaces 5 while maintaining the angle θ, and an interference film filter 6 is provided at the bonding points of the optical fibers 1. The combination of the glass rods 2 and 3 is bonded to a glass rod 4 in which the optical fiber 1 is embedded. In order to operate the optical multiplexer/demultiplexer configured as described above, light of wavelengths λ1 and λ2 is input from the optical fiber 1 of the glass rod 2, and the light of λ2 is transmitted to the glass rod 3 through the interference film filter 6. Further, the light of λ1 is demultiplexed to the glass rods 4, respectively. In the case of multiplexing, conversely, if the lights with wavelengths λ2 and λ are input from the optical fibers 1 of the glass rods 3 and 4, the lights with the frequency wavelengths λ1 and λ2 will be combined from the optical fibers 1 of the glass rod 2. is emitted. As shown in the cross-sectional view of FIG. 2, the glass rods 2 and 3 are connected at an angle θ, and the glass rod 4 is connected through an interference film filter 6 while maintaining an angle of θ/2 with the end face of the above-mentioned combined body. There is.

A third concrete example of the present invention based on the above basic form is described below.
This will be explained using figures. FIG. 3 shows an optical multiplexer/demultiplexer constructed by combining eight glass rods with embedded optical fibers.

The basic rod, which is the basis of the glass rod used in the above structure, has a structure as shown in FIG. After cutting and polishing at an angle such that the surface from the side surface of the glass rod 2 to the center of the embedded optical fiber 1 forms an angle of θ/2 with the axis of the glass rod 2, as shown by the dashed line in FIG. The cut and polished surfaces of these 12 glassrons were aligned and glued together, and then the portion shown by the dashed-dotted line was cut and polished flat, and then the bonded end face was adjusted by tilting θ/2, and the interference film filter 6 was glued. to form the basic rod. When these basic rods are connected and assembled, alignment can be easily performed because they are arranged in the same plane by inputting light into each optical fiber and making adjustments. A suitable size for the glass rod to be easily processed is 2III11 to 5 mmφ, and the optical fiber 1 may be embedded by fusion bonding or bonding.

Glass rod 7.8.9.10 in the embodiment of FIG.
is composed of the above-mentioned basic rod, and is constructed so that the above-mentioned cutting and polishing surfaces are connected to each other. glass rod 11
．． 12, 13, and 14 are used to take out demultiplexed light or input light for multiplexing. 15~ in the same figure
Reference numerals 20 each indicate an interference film filter, which is a bandpass filter that passes light in each desired band.

The operation of the optical multiplexer/demultiplexer of this embodiment is such that the lights of wavelengths λ8, λ2, λ3, and λ4 that are incident from the optical fiber of the glass rod 7 are first largely demultiplexed by the interference film filter 15, and then the lights of wavelengths λ1λ and λ
It is divided into two groups: 2λ. For example, λ,=0.894. λ
3=0.811Im, λ,=1.2-1λ4=1.3
7a.

Then, the wavelength of light transmitted through the interference film filter 15 is 1
．． 2um and 1.3um, the wavelength of reflected light is 0.8
]um and 0.8911m. The light with the wavelength λ1 further passes through the interference film filter 16 and enters the glass rod 11.
The light with a wavelength of λ3 is reflected by the interference film filter 16, passes through the interference film filter 17, and is guided to the optical fiber of the glass rod 14 and extracted.

The interference film filter 17 is used to prevent crosstalk. Wavelengths λ2 and λ on the long wavelength side. The light passes through the interference film filter 15, is reflected by the interference film filter 18, and reaches the interference film filter 19. Interference film filter 1
At 9, light with a wavelength λ of 1.2- is passed through the filter 19 and extracted from the optical fiber of the glass rod 12.

The light having the wavelength λ4 is reflected by the interference film filter 19, passes through the interference film filter 20, and is extracted from the optical fiber of the glass rod 13. The above-mentioned interference film filters 18 and 20 are used to prevent crosstalk, respectively. In this optical multiplexer/demultiplexer, when light with wavelengths λ0, λ2, λ3Jλ4 is inputted from the optical fiber of the glass rod 7, the glass rod 11...
12.14.13 from each optical fiber λ1, λ
2, λ1, and λ4 can be separated and extracted.

Note that by embedding an optical fiber similar to the transmission line in the glass rod, the loss caused by coupling the optical multiplexer/demultiplexer can be significantly reduced.

Furthermore, in the current situation where silica-based optical fibers are used in transmission paths, when forming the optical multiplexer/demultiplexer of the present invention using a basic rod of quartz glass rod with silica-based optical fibers embedded, it is important to ensure that the optical fibers are of the same quality. This reduces waveguide loss, and since the transmission line and the optical multiplexer/demultiplexer are joined by fusion bonding, it is possible to downsize without requiring complicated and large parts such as connectors. When embedding a silica-based optical fiber in a hollow quartz glass tube, the quartz glass tube is heated from the outside with a flame or fused using a heating furnace. When coupling silica-based optical fibers or silica glass rods, carbon dioxide laser,
Alternatively, connect by fusion using an oxyhydrogen burner.

〔Effect of the invention〕

As described above, in the optical multiplexer/demultiplexer according to the present invention, an interference film filter is attached to the end face including the optical fiber branch point of a glass rod in which branched optical fibers are embedded to form a composite optical waveguide. By combining and bonding multiple rods, the assembly process is simple, simply by creating a large number of basic rods and arranging and bonding them in the same plane. Processing is easy because the rod is handled. In addition, coupling loss can be reduced by embedding the same optical fiber as the transmission line, and the optical fiber of the transmission line and the optical multiplexer/demultiplexer can be directly fused together without using bulky parts such as connectors. By combining the above-mentioned effects, such as being able to be made compact for connection, a very economical optical multiplexer/demultiplexer can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the basic principle of an optical multiplexer/demultiplexer according to the present invention, Fig. 2 is a sectional view of the above embodiment, and Fig. 3 is a plan view showing a specific embodiment of the invention. , FIG. 4 is a partial sectional view showing an example of the basic rod constituting the above embodiment. 1... Optical fiber 2.3.4, 7.8.9.10.11.12.13.1
4...Glass rod

Claims (2)

[Claims] (1) A composite optical waveguide is created by embedding a branched optical fiber into a glass rod. An interference film filter is attached to the end face including the optical fiber branch point to form a basic rod, and a plurality of the basic rods are combined to create a composite optical waveguide. Duplexer. (2) The optical multiplexer/demultiplexer as set forth in claim 1, wherein the glass rod is a quartz glass rod and has a silica-based optical fiber embedded therein.