JPH0695174A - Fiber type optical switch - Google Patents

Abstract

PURPOSE:To provide a fiber type optical switch capable of switching a fiber optical path by moving it not mechanically but optically and having high performance and high reliability. CONSTITUTION:Optical coupling parts 1, 2 where both cores 3a, 3b separated by a proper interval are capable of coupling optically with each other are provided on two positions in the longitudinal direction of a two optical fibers 5 in which a first core 3a and a second core 3b are provided in the common cladding 4 so as not to couple optically with each other, and the interval between both optical coupling parts 1, 2 is made a phase difference control area 6. In the phase difference control area 6, when it is impressed by mechanical external force, or physical external force of heat, electricity, magnetism, etc., a difference in a phase shift amt. in light waves propagated through the first core 3a and the second core 3b is controlled, and the core through which a light beam is transmitted between both cores 3a, 3b is made switchable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber type optical switch used for switching optical paths in the fields of optical fiber communication, optical fiber measurement and optical information processing.

[0002]

2. Description of the Related Art As a main type of fiber type optical switch, a conventional type is shown in FIG. The optical fiber 15 is arranged so as to face one of the two optical fibers 16 and 17, and the optical fiber 15 faces the other optical fiber 17 as shown by a chain line in the figure. The fiber 15 can be switched and connected to the fiber 16 or 17 by this movement. In this case, in order to move the optical fiber 15, for example, as shown in FIG.
8 is covered, and the magnetic material 18 is attracted to move the fiber 15 by turning on and off an electromagnet (not shown) provided near it.

[0003]

However, since the conventional fiber type optical switch has the following problems, it is practically difficult to stably and reliably perform the switching operation of tens of thousands or hundreds of thousands or more times. Met. Since the optical fiber 15 moves, the reliability of optical coupling is low. That is, in order to butt-connect a thin optical fiber having a core diameter of about 10 μm or less, such as a single mode fiber, with a low loss, the optical axes of the optical fibers to be connected are accurately aligned, and the distance between the end faces of the optical fibers is also small. It is necessary to make it as narrow as possible and to maintain this state, but it is difficult to realize this with a mechanical mechanism. In the case of high-speed switching, it is necessary to move the optical fiber at high speed, but at high speeds above a certain level, it becomes difficult. The mechanical parts that make up a fiber type switch are required to have high accuracy and high reliability, but there is a limit to that. As the fiber moves, strength fatigue occurs in the optical fiber, and in extreme cases, the optical fiber may break.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fiber type optical switch which can switch the optical path of a fiber without mechanically moving the optical fiber and has high performance and high reliability.

[0005]

The basis of the fiber type optical switch of the present invention is, as shown in FIG. 2, a Maha-Zehnder type interference system composed of optical coupling portions 1 and 2 and a phase difference control region 6. To do. Therefore, as shown in FIG. 1, the fiber type optical switch of the present invention includes a first core 3a and a second core 3a.
The core 3b of the optical fiber 5 provided in the common clad 4 so as not to be optically coupled to each other, at two positions in the longitudinal direction,
Optical coupling portions 1 and 2 capable of optically coupling the two cores 3a and 3b to each other are provided by appropriately separating them, and a phase difference control region 6 is provided between the both optical coupling portions 1 and 2, and the phase difference control region 6 is mechanically connected thereto. By applying an external force or a physical external force such as heat, electricity, magnetism, etc., the difference in the phase shift amount of the light wave propagating through the first core 3a and the second core 3b is controlled, and the two cores 3a, 3b
Among them, the core through which light propagates can be switched. The phase difference control region 6 controls the difference in the amount of phase shift of the cores 3a and 3b between the optical coupling section 1 and the optical coupling section 2. 2A and 2B are input terminals, and C and D are output terminals, which are respectively connected to other fibers.

[0006]

In the fiber type optical switch of the present invention shown in FIG. 2, the light wave incident on the input terminal A is emitted to the output terminal C or D through the following four paths. Light wave A1: input terminal A → optical coupling section 1 → optical path 3a → optical coupling section 2 → output terminal C optical wave A2: input terminal A → optical coupling section 1 → optical path 3b → optical coupling section 2 → output terminal C optical wave B1: input Terminal A → optical coupling section 1 → optical path 3a → optical coupling section 2 → output terminal D light wave B2: input terminal A → optical coupling section 1 → optical path 3b → optical coupling section 2 → output terminal D

The light waves A1 and A2 are superimposed on each other at the output terminal C and interfere with each other. The light waves B1 and B2 are overlapped and interfere with each other at the output terminal D. As a result, the interference intensity Ic at the output terminal C and the interference intensity Id at the output terminal D are obtained by the following equations. Ic = Io sin ² (φ / 2) (1) Id = Io cos ² (φ / 2) (2) where Io is the light intensity incident on the input terminal A, and φ is the phase difference control region 6. This is the difference in phase shift between the cores 3a and 3b. As can be seen from this expression, light is emitted only from the output terminal C when the phase shift is φ = π / 2, and is emitted only from the output terminal D when the phase shift is φ = 0. Therefore, the optical path is switched by controlling the phase shift φ. That is, by controlling the magnitude of the phase shift φ in the phase difference control region 6, 2 × 2 light output is switched between the input terminals A and B and the output terminals C and D. In this description, the optical coupling unit 1,
Although 2 is a 3 dB coupler, the magnitude of the coupling ratio of the optical coupling sections 1 and 2 is essentially unrelated to the optical path switching operation.
Only the magnitude of the phase shift required to switch the optical path differs from that described above.

[0008]

First Embodiment In FIG. 1 (a) showing a first embodiment of the fiber type optical switch of the present invention, 5 is an optical fiber or a rod, which comprises two cores 3a and 3b,
It is composed of a common clad 4 surrounding them. First core 3a and second core 3b (two waveguides)
The propagation constants βa and βb of are the same. When no processing is applied to the optical fiber 5, the first core 3a and the second core 3b are not optically coupled. This optical fiber 5 is stretched, for example, in a heated and softened state to be tapered as shown in FIG. 1A, and that portion can be optically coupled between the first core 3a and the second core 3b. An optical coupling portion (which functions as an optical coupler) is formed. Further, a phase difference control region 6 is formed between the both optical coupling portions 1 and 2.

The phase difference control region 6 includes the first core 3a and the second core 3a.
Is a region where light transmitted through the core 3b is not coupled, and is a region for controlling the phase difference between the light waves guided through the first core 3a and the second core 3b. To control the phase difference in the phase difference control region 6, for example, as shown in FIG. 1B, an electric current is applied to the metal plate 7 provided on the outer circumference of the optical fiber 5 to thermally expand the metal plate 7, Thereby, the optical fiber 5 is bent in the zx plane as shown in FIG. At this time, when the distance between the two cores 3a and 3b is 2S, the length of the phase difference control region 6, that is, the portion where bending is applied is L, and the radius of curvature thereof is R, the cores 3a and 3b are manufactured with the same structure. Therefore, the phase difference φ between the two waveguides is given by the following equation. φ = β · 2S · (L / R) β is a propagation constant, and β = βa = βb. Normal core /
In the case of a fiber having a refractive index difference Δn = 0.3% of the clad, it is approximated as β = (2π / γ) n1. n1 is the refractive index of the core, which is about n1 = 1.46 for silica-based glass. If S = 125 μm, the phase difference can be controlled within a sufficiently large range of several rads with a slight bend of about L / R = 0.01. Actual core / clad refractive index difference Δn = 0.3%, n1≈1.46, core diameter 9
A quartz fiber having a diameter of μm and a cladding outer diameter of 250 μm was produced, and the fiber type switch shown in FIG. The length of the phase difference control region 6 is L≈10 m
As m, a metal plate 7 was attached to this portion as shown in FIG. 1B, and a current was passed through the metal plate 7 to confirm the function of the optical switch.

[0010]

[Second Embodiment] FIG. 3 shows a fiber structure of a second embodiment of the fiber type optical switch of the present invention. Reference numeral 5 in FIG. 3 denotes an optical fiber, which comprises a core 3a and a core 3b, and a common cladding 4 surrounding them. Core 3a and core 3
b has a different core diameter or refractive index. In this case, the propagation constants βa and βb of the light waves propagating through the core 3a and the core 3b (two waveguides) are different. When a fiber type optical switch having the same configuration as the fiber type optical switch shown in FIG. 1A is manufactured using such an optical fiber 5, when controlling the phase difference in the phase difference control region 6, It is not necessary to bend the optical fiber 5 as in the case. Since the phase difference is given by the following equation, φ = (βa−βb) · L, means for changing βa−βb or changing L can be used. As a means for changing βa-βb, there is a photoelastic effect by pressure, and as a means for changing L, tension, thermal expansion, etc. can be used. Actually, a fiber type optical switch similar to the fiber shown in FIG. 1A is configured by using the fiber shown in FIG.
The phase difference control region 6 was coated with a piezoelectric material, a voltage was applied to the piezoelectric material, and the function of the optical switch was confirmed by utilizing the photoelastic effect due to the pressure generated in the piezoelectric material at that time.

[0011]

Third Embodiment FIG. 4 shows the fiber structure of a third embodiment of the fiber type optical switch of the present invention. Reference numeral 5 in FIG. 4 denotes an optical fiber, which comprises a core 3a and a core 3b, and a common clad 4 surrounding them. The cores 3a and 3b have the same structure, but the core 3b is provided at the center of the clad 4, and the other cores 3a are provided at positions eccentric from the center of the clad 4. In this case, βa = βb, but both cores 3a,
Since the position of 3b is different, both cores 3 when external force is applied.
The degree of force applied to a and 3b is different. That is, both cores 3
Since a and 3b differ in the degree to which they receive the photoelastic effect due to pressure, when an external force is applied, βa ≠ βb and the phase difference φ = (β
a-βb) · L can be controlled.

[0012]

The fiber type optical switch of the present invention has the following effects. ． Since the fiber is not mechanically moved, the structure is simple, the damage and fatigue of the fiber do not easily occur, and the reliability is high. The cost is also low. ． Since it is optical switching, the precision of optical axis alignment at the time of switching is higher than that of mechanical switching, and connection loss associated therewith does not occur. ． Optical switching enables high-speed response.

[Brief description of drawings]

FIG. 1A is a perspective view showing an embodiment of a fiber type optical switch of the present invention, and FIG. 1B is a partial explanatory view showing a state where a phase difference control region of the switch is curved.

FIG. 2 is a principle diagram of a fiber type optical switch of the present invention.

FIG. 3 is a perspective view showing a second example of a fiber in the fiber type optical switch of the present invention.

FIG. 4 is a perspective view showing a third example of a fiber in the fiber type optical switch of the present invention.

FIG. 5 is a schematic view showing an example of a conventional fiber type optical switch.

[Description of Reference Signs] 1 optical coupling section 2 optical coupling section 3a first core 3b second core 4 clad 5 optical fiber 6 phase difference control region

Claims (1)

[Claims] 1. A first core 3a and a second core 3b are provided in a common clad 4 at two positions in a longitudinal direction of an optical fiber 5 provided so as not to be optically coupled to each other, and both cores 3a are appropriately separated from each other. 3b is provided with optical coupling portions 1 and 2 capable of optically coupling with each other, and a phase difference control region 6 is provided between both optical coupling portions 1 and 2.
The phase difference control region 6 applies a mechanical external force or a physical external force such as heat, electricity, and magnetism to the difference between the phase shift amounts of the light waves propagating through the first core 3a and the second core 3b. A fiber type optical switch characterized in that the core through which light propagates among the two cores 3a and 3b can be controlled to be switched.