JPH0261721B2 - - Google Patents

Description

Detailed Description of the Invention This invention provides a demultiplexing function that separates light of a plurality of different wavelengths propagating through one optical transmission line into independent directions, and a demultiplexing function that separates light of a plurality of independently different wavelengths into a single optical transmission line. This invention relates to an optical wavelength demultiplexing/multiplexing device using an interference filter having a multiplexing function for inputting to an optical transmission line.

FIG. 1 shows an example of an optical wavelength demultiplexing/multiplexing device using a conventional interference filter. In FIG. 1, the end surfaces of each optical fiber 1a to 1e are connected to each lens 2a to 2e.
is placed in the focal plane of 3a is a long wave pass filter (hereinafter referred to as LWPF) that transmits light with a wavelength of 1.3 μm band and reflects light with a wavelength of 0.8 μm band, and 3b transmits light with wavelength λ ₁ and reflects light with other wavelengths. A bandpass filter (hereinafter referred to as BPF) 3c is a BPF that transmits light of wavelength λ ₃ and reflects light of other wavelengths, and is installed oriented toward the incident light. Here, the lights with wavelengths λ ₁ and λ ₂ are in the 1.3 μm band, and the lights with wavelengths λ ₃ and λ ₄ are in the 0.8 μm band. Currently, the wavelength bands that can realize optical wavelength division multiplexing transmission are the 0.8 μm band and the 1.3 μm band, and such an optical wavelength demultiplexing/combining device that covers both wavelength bands is useful. In such a configuration, when performing demultiplexing, the following operation is performed. Light with wavelengths λ ₁ to _{λ 4} propagates through the optical fiber 1a. Since the transmission characteristics of the interference filter change depending on the incident angle of the light beam, the light having wavelengths λ ₁ to _{λ 4} emitted from the fiber 1a is converted into a parallel light beam by the lens 2a and enters the LWPF 3a.
Here, light with wavelengths λ ₁ and λ ₂ in the 1.3 μm band is transmitted, and 0.8 μm
Light with wavelengths λ ₃ and λ ₄ in the m band is reflected. The transmitted lights with wavelengths λ ₁ and λ ₂ enter the BPF 3b, where the wavelengths λ _{1 and} λ 2
The light of wavelength λ ₂ is reflected and focused onto the optical fiber 1c by the lens 2c.

On the other hand, the light with wavelengths λ ₂ and λ ₄ reflected by LWPF3a is
Through a process similar to that described above, the light with wavelength λ ₃ is input into the optical fiber 1d, and the light with wavelength λ ₄ is input into the optical fiber 1e. As mentioned above, the wavelength λ ₁ to _{λ 4}
The light of wavelengths λ 1 to λ 4 is demultiplexed, but the light of wavelengths λ ₁ to _{λ 4} is combined by reversing the optical path described above.

As described above, in this configuration, the five input/output ports are arranged in a scattered manner. Therefore, in the optical wavelength demultiplexing/multiplexing device with the conventional configuration described above, when adjusting the coupling of light between the optical fibers of each port, each optical fiber, each lens, and each interference filter must be adjusted independently. This has the disadvantage that the alignment adjustment is complicated.

In order to eliminate this drawback, the present invention arranges a prism block array, a lens array, and an optical fiber array, which are designed so that all of the light that has been demultiplexed with respect to the incident light is emitted in the same direction, without the need for adjustment. This was an attempt to realize an optical wavelength demultiplexing and multiplexing device.
The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is a diagram showing an embodiment of the present invention.
In the figure, a prism block array 4, a lens array 5, and an optical fiber array 6 are arranged in order on a plane. The prism block array 4 is constructed by arranging prism blocks 7a, 7b, and 7c of the same shape in a line. The lens array 5 is constructed by arranging spherical lenses 8 having the same diameter in a line, assuming that spherical lenses are used here. The optical fibers 1a to 1f are each housed in a precision nozzle 9 that has a hole drilled in the center with respect to the outer diameter, and the optical fiber array 6 arranges the precision nozzles 9 containing the optical fibers in a line with their end faces aligned. It consists of: Here, the outer diameter of the ball lens 7 and the outer diameter of the precision nozzle 8 are the same, and the prism blocks 7a, 7b,
It is equal to 1/2 the length of the base 10 of 7c.

Here, the function of the prism block array 4 will be explained. FIG. 3 is a diagram illustrating the operation of a single prism block constituting a prism block array. The prism block 7 is composed of two identical prisms 11a and 11b glued together, and an interference filter 12 is formed on the boundary surface. These prisms 11a and 11b have two angles θ ₁ and θ ₂ shown in FIG. 3 and a refractive index of the prism material.
The following relationship is satisfied between n ₁ and the refractive index n ₂ of the surrounding medium. Note that FIG. 3 shows the case where θ ₂ =90 degrees.

π=3θ ₁ +θ ₂ sin ^-1 (n ₂ /n ₁ ) -sin ^-1 (n ₂ /n ₁ sinθ ₁ ) ......(1) θ ₁ +θ ₂ -π/2+sin ^-1 (n ₂ /n ₁ cosθ ₂ )＜cos ^-1 n ₂
/n ₁ ...(2) At this time, the operation of the prism block 7 is as follows. In this prism block 7, the port
The light incident from P ₁ is on the slope 13 of the prism 11a.
The light component that is totally reflected at the interference filter 12 and reflected by the interference filter 12 is refracted at the slope 13 of the prism 11a, and the light component that is transmitted through the interference filter 12 to port _P2 is reflected by the prism 11b. The light beams are refracted at the slope 14 and emitted to the port _P3 . Further, the light incident from port _P2 is refracted at the slope 13 of the prism 11a and enters the interference filter 12, and the light component reflected by this interference filter 12 is totally reflected at the slope 13 of the prism 11a. port
The light component that passes through the interference filter 12 toward _P1 is totally reflected on the slope 14 of the prism 11b, and then exits to the port _P4 . Here, all of the emitted light is emitted in a direction perpendicular to the light that enters the prism block 7. In addition, when the input port is P ₁ , the two demultiplexed lights are symmetrically emitted in opposite directions with respect to the interference filter surface 12, and the input port is P ₂ and
In the case of P ₃ , the two demultiplexed lights are emitted in parallel to each other in the same direction.

Next, the prism block array 4 in which these prism blocks are arranged will be explained. Here, the demultiplexing of light of the four wavelengths λ ₁ and λ ₂ in the 1.3 μm band and wavelengths λ ₃ and λ ₄ in the 0.8 μm band will be described. FIG. 4 is a diagram explaining the operation of the prism block array. Each prism block 7a, 7b, 7c
are equipped with interference filters 12a, 12c, and 12c, respectively. Prism block array 4
is constructed by arranging these prism blocks 7a, 7b, and 7c so that their surfaces 12a, 12b, and 12c are opposite and parallel to each other. The interference filter 12a transmits light in the 1.3 μm band, and transmits light in the 0.8 μm band.
LWPF that reflects the band light, interference filter 12b
is a BPF that transmits light of wavelength λ ₁ and reflects light of other wavelengths, and interference filter 12c is a BPF that transmits light of wavelength λ ₃ and reflects light of other wavelengths.
In such a configuration, each prism block 7a,
Since 7b and 7c operate as shown in FIG. 3, the wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ incident from port P ₁
The light is branched and emitted to ports P ₂ , P ₃ , P ₄ , and P ₅ , respectively. At this time, all five ports _P1 to _P5 are in the same order in the prism block array 4,
The two incident lights and the outgoing lights are parallel to each other. Let us now look at the relationship between the incident position of light on prism block 7a and the output position of light from prism blocks 7b and 7c. Take the X coordinate as shown in Figure 4, and define the light input and output positions at ports _P1 to _P5 as X _P1 to
Let it be X _P5 . At this time, each prism block 7a,
If the length of the base of the prisms 11a and 11b constituting prisms 7b and 7c is L, and the distance from the interference filter 12a to the position of incidence of light on the prism block 7a at port _P1 is d, the input and output positions of each light are is X
The coordinates can be expressed in order from the left using the following formula. X _P4 =L-
d, _P5 = L+d, X _P1 = 3L-d, X _P3 = 5L-d,
X _P2 = 5L + d Also, looking at the distance between each port, X _P5 −X _P4 = 2d, X _P1 −X _P5 = 2L−2d, X _P3 −X _P1
= 2L, X _P2 −X _P3 = 2d. If we set d=1/2L, the above equations become X _P5 −X _P4 = L, X _P1 −X _P5 =
L, X _P3 −X _P1 = 2L, and X _P2 −X _P3 = L, and the intervals between each port are all L except for one where it is 2L, and they are equally spaced. Therefore, the optical fibers for inputting and outputting light and the optical coupling lenses are spaced at equal intervals L.
The optical axis can be adjusted simply by arranging them. An embodiment of the present invention shown in FIG. 2 is constructed in this manner. As mentioned earlier, the outer diameters of each lens 8 and each fiber-internal precision nozzle 9 are equal, and furthermore, the length of 1/2 of the base 10 of the prism blocks 7a, 7b, 7c, that is, the length of the base of the prisms 11a, 11b. Equal to L. Therefore, if all the components are aligned with reference to the X-axis 14 and Y-axis 15, all optical axis adjustments will be automatically completed. Here, the precision nozzle 16 incorporating the optical fiber 1f and the ball lens 17 are dummies for narrowing the above-mentioned distance 2L. In this way, the optical fiber 1a
The light beams of wavelengths λ ₁ , λ ₂ , λ ₃ , λ ₄ that have been propagated through the optical fibers 1b, 1c, 1c,
The light is input to 1d and 1e, and the light is demultiplexed.
Further, the multiplexing of the lights of wavelengths λ ₁ to _{λ 4} is performed by reversing the optical path described above.

As described above, the optical wavelength demultiplexing/multiplexing device with this configuration has the advantage that the optical axis adjustment between the input and output optical fibers of each port can be performed without adjustment simply by lining up each component. . Another advantage is that the structure is compact and can be made small.

Although the above description has been about an optical wavelength demultiplexing/multiplexing device that demultiplexes and multiplexes light of four wavelengths, the present invention is not limited to this. Light of two wavelengths is first separated at a certain intensity ratio, and then each It may also be used in an optical branching/demultiplexing device that splits light into two wavelengths.

As described above, in the optical wavelength demultiplexing/multiplexing device according to the present invention, the angles θ ₁ and θ ₂ and the refractive index n ₁ of the prism,
Between the refractive indices n ₂ around the prism, π=3θ ₁ +θ ₂ sin ^-1 (n ₂ /n ₁ ) −sin ^-1 (n ₂ /n ₁ sinθ ₁ ) and θ ₁ +θ ₂ −π/2+sin ^-1 (n ₂ /n ₁ cosθ ₂ )＜cos ^-1 n ₂
Two triangular prisms having a relationship of /n ₁ are joined so that they face each other on the plane between the angles θ ₁ and θ ₂ , and are symmetrical about the above plane, and at this time, a multilayer film interference filter is placed on this joint surface. A prism block array in which a plurality of prism blocks forming a prism block are arranged in a line, a lens array in which a plurality of lenses are arranged in a line, and an optical fiber array in which a plurality of optical fibers are arranged in a line are arranged on a plane. This allows optical axis adjustment to be made without any adjustment. Another advantage is that the overall configuration can be made compact.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional optical wavelength demultiplexing/multiplexing device.
Figure 2 is a configuration diagram of one embodiment of the device of this invention;
Figure 4 is a diagram explaining the operation of the prism block.
The figure is a diagram explaining the operation of the prism block array. In the figure, 1a to 1e are input and output optical fibers, 2a to 2
e is lens, 3a is LWPF, 3b, 3c are BPF,
4 is a prism block array, 5 is a lens array, 6 is an optical fiber array, 7, 7a, 7b, 7
c is a prism block, 8 is a ball lens, 9 is a precision nozzle, 10 is the bottom of the prism block, 11
a, 11b are triangular prisms, 12 is an interference filter, 13a is a slope of the triangular prism 11a, 13b
is the slope of the triangular prism 11b, 14 is the X axis, 15
is the Y axis, 16 is a dummy precision nozzle, and 17 is a dummy ball lens. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1 The angles of two of the three corners of the prism are θ ₁ and θ ₂ , the refractive index of the material of the prism is n ₁ , the refractive index of the medium surrounding the prism is n ₂ , and the above θ ₁ , θ ₂ and
Between n ₁ and n ₂ , the following formula π=3θ ₁ +θ ₂ +sin ^-1 (n ₂ /n ₁ COSθ ₂ ) -sin ^-1 (n ₂ /n ₁ sinθ ₁ ) ......(1) θ ₁ +θ ₂ −π/2+sin ^-1 (n ₂ /n ₁ cosθ ₂ )＜cos ^-1 n ₂
/n ₁ ……(2) or two prisms that almost satisfy the above relationship are arranged to face each other on the plane between angles θ ₁ and θ ₂ so that they are symmetrical on the above plane. A prism block array in which a plurality of prism blocks each having a multilayer film interference filter formed on the joint surface are arranged in a row so that the joint surfaces are parallel to each other and facing each other, and a plurality of lenses are arranged so that the optical axes thereof are parallel to each other. It consists of a lens array arranged in a row parallel to each other, and an optical fiber array in which a plurality of optical fibers are arranged in a row with their end faces aligned, the prism block array, the lens array,
An optical wavelength demultiplexing/combining device characterized in that the optical fiber arrays are arranged on a plane in the order described above with the end faces of the arrays facing each other.