JPS62106419A - Optical fiber connector - Google Patents

Abstract

PURPOSE:To obtain an optical fiber connector of less reflection loss by forming front end parts of a cores of the optical fiber connector with zirconia ceramics and forming front ends of cores into convex faces and applying a sufficient pressing force to front end parts butted at a connection time. CONSTITUTION:Core front end parts 3 and 3' inserted to a split sleeve 7 consist of zirconia ceramics and are integrated with core metallic parts 4 and 4' into one body. In case that the connector is assembled, front end parts 3 and 3' are fitted from both sides of an adapter 6, and coupling nuts 8 and 8' and the adapter 6 are screwed. Thus, a pressing force in the direction of a coupling axis is applied to core front end parts through collars of core metallic parts by springs 5 and 5'. Front ends of cores are ground into convex faces.

Description

Detailed Description of the Invention (Industrial Application 1M1) The present invention relates to a removable optical fiber connector used in a transmission line using optical fibers, in which light reflection at the connector joint is a problem. This optical fiber connector is useful for use in connection points such as:

(Prior art) When connecting optical fibers to each other using an optical fiber connector, reflected light is generated at the connection point, and when it enters a light source such as a laser diode, the oscillation operation of the light source becomes unstable and noise is generated. occurs. Therefore, there is a need for an optical fiber connector that produces less reflected light at the connection point. Conventionally, as a method of reducing this reflected light, there has been a method of putting matching oil, resin, etc. into the connection part, but the structure, connection work, etc. are the subject matter. On the other hand, Tokukai Akira! ≠-/J-7633, Ko I
s λ The tips of the two optical fibers are each processed into a spherical surface with a radius of curvature of 2 (γ. + 7) (where λ - the optical wavelength, ro - the core radius of the optical fiber) or more, and the ends of both fibers are brought into point contact with each other. A fiber optic connector is described. In such optical fiber connectors, the conditions for reducing reflection are that the cores of the optical fibers make point contact with each other, and that when they make contact, the distance between the cores is about the wavelength of the light being used. It is said that

However, in actual optical fiber connectors, the end face of the optical fiber is different from the end face of the core due to differences in the coefficients of thermal expansion between the optical fiber and the core, changes over time in the adhesive that fixes the optical fiber in the core, etc. A phenomenon of retraction occurs, making it difficult to realize a pongee in which the fiber cores are in point contact. FIG. 3 shows, as an example, the actual measurement results of the amount of retraction of the optical fiber when a warm armpit rise is applied to a CERAOC core to which the optical fiber is fixed. Approximately 0.02 μ when the temperature rises to”c
There is a fiber retraction of m. In order to prevent the fiber from retracting even when the temperature changes, it is possible to use a core material such as quartz that has the same coefficient of thermal expansion as the optical fiber, but these materials are generally It is weak and unsuitable as a core. On the other hand, as a result of considering the requirement that the gap between the core ends of both fibers be equal to or less than the optical wavelength, we found that λ
It has become clear that, in contrast to multiple reflections, there is a point where the reflection is maximum where the gap f between the two ends corresponds to approximately the wavelength of the light.

[Problem that the invention seeks to solve]

The present invention aims to realize an optical fiber connector with low reflection loss by taking into account the drawing of the fiber into the core and keeping the core spacing of the optical fibers at a certain value or less during connection. be.

(Means for Solving the Problems) The present invention includes forming at least the tip of the core of the optical fiber connector from zirconia ceramic, which is a relatively soft material, and forming the tip of the core into a convex spherical surface. .

In such a connector, an optical fiber connector with low reflection loss is realized by applying a sufficient pressing force to the abutting ends at the time of connection.

(Function) The following study was conducted regarding the allowable value of the core end face gap V when connecting optical connectors. Figure M≠ is a model diagram for determining the reflection at the fiber end face.

The M refractive index of Coata and Ri' is no=7.4A7. A high refractive index layer /8//' is formed on the end face of an optical fiber as the fiber surface is polished (References 3, et al., IEICE Tomo Vol.
J is 7-B, A/, 2, /#4'). The refractive index of this high refractive index layer is nl=/, the 11% thickness is t-0,
The diameter was assumed to be 0.03 μm. At this time, the refractive index of the core gap 10 is n@ = x / the gap is 11 the power of the incident light is Pi1 the power of the reflected light is Pr.

When the transmitted light power is pt and the wavelength of light is λ, the reflectance R and transmittance T of the optical power are expressed by the following equations.

'p= /-R(2+ Here, the return loss α is α=-10 gloR(dB) (
6). No.! In the figure, λ-0, Ijr, /, 3
．． /, subtract α for f for tμm. In current optical communication systems, α is at least 20 dB or more4! - Since it is necessary, in order to satisfy this, 2 is α-0,112m
It is sufficient if it is about 0, Ojpm or less at /, 3pm or less, about 0.07pm or less at 7.4pm, and about o, oyμm or less at 7.4pm.

(Example) Figure 1 shows an example of the present invention.
-' is core metal part 1. t and j' are springs, O is an adapter, 7 is a split sleeper, and t and r' are coupling nuts. In this embodiment, the core tip 3.3 inserted into the split sleeve 7 is entirely made of zirconia ceramic material, and is integrated with the core metal part G.t'. In this way, the zirconia ferrule (metallic part of the tip) is made by polishing the outer periphery of the ceramic part after mixing the raw materials, molding it, and forming a precision hole into which the fiber will be inserted. This is then press-fitted into the metal part.
Zater/, 2).

To assemble this connector, insert the tips 3 and 3' of the adapter B from both sides, and screw the coupling nuts r and t to the adapter 6. It's good to do it like this, spring! , j' apply a pressing force in the direction of the joining axis to the tip of the core through the collar of the core metal part. In this embodiment, the tip of the core is polished to a convex surface with a radius of curvature j011m.

Figure 2 is an enlarged view of the tip of the core of the connector when mating.Since the tip is convexly polished, the entire tip of the core does not come into contact, but due to the fiber pull-in phenomenon described earlier, , a minute interval t occurs between the fiber end faces. In such a state, by applying a pressing force by the springs j and j', the ferrule tip is slightly deformed, and the distance between the end faces is reduced to less than the above value, thereby attenuating the reflection at the end face. This makes it possible. Figure 2 shows an example of the change in return loss when a pressing force is applied in the axial direction between the 7-engine rules in the form of Figure 2. The sum of the fiber retraction amounts of both ferrules is approximately 0. /p
m, the measurement fiber is a graded index fiber with a core diameter of Opm, and the wavelength is o, rsμm.

In the connector of the embodiment shown in FIG. 1, the Young's modulus of the zirconia used as the ferrule is approximately θθθh/wJ (black circle), and the pressing force is 0. /Ay or more, return loss is 20
dB or more can be achieved. On the other hand, when an alumina ferrule (Young's modulus of 1/-0000 h/J) is used (white circle), a pressing force of O2≠2 or more is required to obtain the same amount of return loss. Here, the pressing force applied to the tip of the ferrule is generated by a spring provided at the rear of the core, but the ferrule is resisted by the holding force of the 1llX rib 7. This holding force is approximately 0.41 kyf,
Considering the fact that the connector uses Alden Nacera 2x, even if a pressing force of /kv is applied, if the fiber is pulled in even more due to changes in the environmental temperature, etc. There is a high possibility that reflection loss will deteriorate. On the other hand, the optical connector of the present invention has sufficient tolerance in terms of pressing force/displacement and is less likely to deteriorate over time.

(Embodiment 2) Fig. 7 shows another embodiment of the core that can be used in the optical fiber connector of the present invention.The core body 33 is made of metal (stainless steel, etc.)
Three ceramic capillaries are embedded in the tip of the capillary. To make this core, step 9! The box part is manufactured through a process of mixing raw materials, molding, and forming a precision hole for inserting the fiber, and is press-fitted into the metal part of the core body, which has been processed separately. Next, 1 capillary 3≠
The outer periphery is polished around the center hole to complete the core.

If a zirconia ceramic tip is used as the capillary 3 and the tip of the core is polished to a convex surface, the same effects as in the first embodiment can be obtained by using the same components as in the M/ embodiment other than the core. It is possible to create a single connector with

(Effects of the Invention-*) As explained above, in the optical 7-eyeper connector of the present invention, by applying a pressing force of approximately lkf in the direction of the joint axis of the core, the line between the core end surfaces of both 7-eyeper The wavelength of the light passing through the distance can be made sufficiently small, and an optical fiber connector with reduced reflected light can be obtained without using a mating material between both fiber end faces.

In addition, this pressing force can be easily achieved with a general spring, and the effect of deformation of the ferrule tip has sufficient tolerance against fiber pulling, which can actually occur. , it is possible to form an optical fiber connector with little deterioration over time.

[Brief explanation of drawings]

FIG. 7 is a configuration diagram of the optical fiber connector of the present invention, the second
The figure is an enlarged view of the tip, Figure 3 is the actual measured value of the amount of fiber retraction due to temperature change, Figure 3 is a model diagram for determining the reflection at the fiber end face, and Figure 1 is the return loss and 7 FIG. 7 is a diagram showing the relationship between the eye spacing, FIG. 7 is a diagram showing the relationship between return loss and ferrule pressing force, and FIG. 8l'...Optical fiber, 2.2'...Target, 3
．． 3'...-lO- Core tip, μ, V'... Core metal part, i J-'.
...Spring, 2...Adapter, 7...Split sleep,
♂? ...Coupling nut, Ri...Fiber core, IO...Gap, /to//'...High refractive index layer,
33... Core body, 3 Hiro... Capillary.

Claims (1)

[Claims] The ends of two optical fibers to be joined are each fixed in a core, and the cores are butted together in a sleep so that the ends of the optical fibers are axially aligned and connected to each other. In the optical fiber connector, the core has a mating surface formed as a convex spherical surface, at least the mating surface is made of zirconia ceramic, and has means for applying a pressing force in the direction of the joint axis to the core at the time of joining. An optical fiber connector featuring: