JPS58107512A - Optical control fiber element - Google Patents

Abstract

PURPOSE:To vary the light volume which is transmitted by an optical fiber with a simple constitution, by providing a heating material on the outer circumferential surface of the optical fiber. CONSTITUTION:An electro-resistance thin film 2 of Ni-Cr, etc. is formed on a single surface (a) or entire surface (b) of a quartz optical fiber 1 by a vacuum deposition, sputtering and other processes. The temperature of the thin film 2 is raised up by the current pulse to heat the clad part. This increases the refractive index and decreases the light volume transmitted in the fiber 1. As a result, the ON/OFF is possible for the light in response to the current signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a completely linear optical modulation element that can change the amount of light transmitted through an optical fiber by thermally controlling the optical fiber.

2. Description of the Related Art Optical modulators, including optical shutters, for controlling light intensity using signals have recently been rapidly developed in optical communications and other fields. The conventional light modulation element is gadolinium-iron garnet (Gds-x Bix F
e5-y Gay 012) Qi crystals or epitaxial films are placed in a magnetic field to control light using the 7 Arede effect, and light is controlled using the Kell effect that often occurs when an electric field is applied to a PLZT plate. However, these light modulation elements require a polarizer and an analyzer to assemble the light modulator, and the fabrication of large-area elements is currently difficult. It is impossible to do so, and the bender needs to apply a lo o Qe Yanghen magnetic field under a higher degree than the auxiliary device, and the latter also has the disadvantage of a high trace voltage of 80-250V.

On the other hand, optical fibers are small diameter, lightweight, durable, electrically insulated, non-inductive, fireproof, water resistant, corrosion resistant, wideband, and have recently been developed with other features such as 'Fi low loss ratio'. Numerous ■ Excellent % songs have been developed, not only in the communication field, but also in f, 4.
O In many fields, there are one or two uses of θ.

However, the conventional usage example is only to use υ as an optical waveguide, and when modulating the guided light, it is taken out of the first fiber and modulated, and in some cases, the modulated light is input into another optical fiber. It had the disadvantage that it had to be done.

The present invention provides an extremely simple structure by providing a minute heating element outside the optical fiber 7 1111rIi and changing the refractive index of the cladding part of the optical fiber due to temperature changes, thereby causing light to leak from the core part. Depending on the structure, it is possible to change the propagation force of the fiber and give it the function of an optical modulation element. A detailed explanation will be provided based on examples.

Optical fibers can be broadly classified into two types based on their structure. Figure 1 shows 7 dos vc
@Step-type original fiber whose refractive index changes in a step-like manner and graded-type 7 Eyepa+, whose refractive index changes in a parabolic Kf direction in the half direction, but in any case, the core The refractive index of the fiber center till is slightly smaller than the outer periphery mL2D @ refractive index (0,1~
1%), and the light waves are confined in the core and propagate.

In terms of structure, the optical fiber can be divided into quartz-based fiber, multi-component optical fiber, and plastic-clad optical fiber, but in the present invention, quartz-based fiber is used. In a quartz-based original fiber, the core is quartz glass doped with GeO2, P2.05, etc.

The cladding is made of quartz glass doped with B2O5 or the like.

If the refractive index of the core is no% and the refractive index of the cladding is nc, then the refractive index difference Δ is n.

Defined by As mentioned above, Δ is usually chosen to be α1~l, where Δ=0. U U 5, no = 1.46
In the case of a quartz fiber with a diameter of 0, n(!-1,453), and the difference in refractive index between the 5 core and the cladding is on the order of lO to 10 O.

By the way, in a dielectric medium such as glass, the refractive index changes depending on the temperature [K], and in the temperature range of 0 to 100°C, the refractive index changes by 10-5°C in the case of glass.

Figure 2 shows the temperature dependence of the refractive index of silica glass. According to this, by heating from room temperature to 300℃, 4X1 (
It can be seen that a change in the refractive index of J occurs. Therefore, if this degree of υ change is applied to the cladding, its refractive index becomes approximately equal to the core O refractive index. Under such conditions, the guided light propagating within the core of the optical fiber is confined in the core and cannot propagate, and leaks into the cladding. The light leaking to the cladding part is
! ! Even if it is reflected by a surface, the light will not become guided into the core again and will be emitted to the outside of the optical fiber. Therefore,
If a heating part is provided in a part of the optical 7-eyeper and the fiber is heated in accordance with an input signal, the fiber can be used as an optical switch or an optical modulation element in which the guided light intensity decreases with heating.

The heating section described above can be made by forming a heating element, such as an electric resistor thin film, on the outside of the optical fiber by vacuum deposition or sputtering. Ni-Cr,
Various materials can be used for this purpose, including thin films as well as RuO
A single film resistor such as 2 may also be used. ・Selectively place such a resistor 2 on one side rM (angle or the entire outer periphery (b) of the fiber L as shown in Fig. 113 by photo-etching, etc.) A resistive element having a resistance of Ω to several Ω is used.This resistive element generates heat by a current pulse, and it is possible to raise the temperature to 300° C. to 500° C. by a current pulse of several μ3 to several m5f. The cladding part is heated due to this temperature rise, and the light that was guided inside the optical fiber leaks to the outside as described above.

When observing the light intensity at the output end, it is seen that the light intensity changes υ according to the current pulse, as shown in FIG. That is, it becomes possible to turn the light ON and OFF according to the current signal. There are two types of fiber: multi-mode fiber and low-mode fiber.The core of multi-mode fiber is around 60 mm.
-Many one-mode fibers are around 5IJxn υ, and the typical cladding diameter is 150IIm, but in any case, the heat capacity is sufficiently small and the optical response is 1 mm.
It is possible to do the following.

FIG. 5 shows an optical switch array constructed by connecting a plurality of optical fibers as described above. By arranging the fibers 1 on a substrate 3 that acts as a heat sink and independently providing a resistance element 2 to each fiber, it is possible to selectively control any fiber. Depending on the case, resistors can be provided all at once, but in this case all the fibers will be operated at the same time.

In the above embodiment, the resistor is energized to generate heat, but other suitable types of heating elements may be provided, for example, by providing a thin film of material O with high absorption rate to raise the temperature by absorbing light. Needless to say, it is okay.

As explained above, the present invention provides an element DII by simply forming a thermal element on the precious or outer circumferential surface of an optical fiber.
It is not only easy to construct and manufacture, but also when used as an optical modulator, there is no need to extract the guided light of the fiber to the outside and perform KM. No other optical elements are required. Furthermore, since the fiber itself is a waveguide, there is no need to create an external waveguide to configure the optical quality 1lI11 as in the conventional case.

It can also provide a very simple optical switch. Since the device is extremely small, it can be used as an optical shutter array by combining multiple fibers, and has a wide range of applications including the field of optical communication as an optical modulator that goes beyond conventional methods.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the structure of an optical fiber, Fig. 2 is a fiber material Il) temperature-refractive index change curve, Fig. 3 is a perspective view of an embodiment of the optical control fiber of this invention, and Fig. 4 is its operating situation. The explanatory diagram and the IM5 diagram are conceptual diagrams of the structure of the optical switch array. 1: Optical fiber 2: Heat generating resistor 3: Substrate patent applicant Chin Shiki Huishi Ricoh

Claims (1)

[Claims] An optical fiber control element characterized by 4I that a heating body is provided on the outer peripheral surface of the optical fiber.