JPH0797166B2 - Optical feed - Google Patents

Description

Description: (1) TECHNICAL FIELD The present invention relates to a structure of an optical feedthrough in an optical fiber introducing portion to a repeater housing of a submarine optical cable transmission system.

(2) Prior Art and its Problems FIG. 1 shows an example of the configuration of a repeater of a submarine optical cable transmission system. Here, 1 is a submarine optical cable, 2 is a T-T connection part, 3 is an optical feedthrough, 4 is a repeater circuit, 5 is an end face plate, 6 is a pressure-resistant housing, 7 is an optical fiber, and 8 is an optical fiber fusion bonding. The connecting portion 9 is a cable retractor.

The repeater may be laid on the seabed up to a depth of 8000m, and the optical feedthrough 3 is excellent in water pressure resistance against high water pressure up to 800 atm and keeps the humidity inside the pressure-resistant housing 6 low for a long time. Airtightness is required,
It is necessary to introduce an optical fiber into the repeater circuit 4 without degrading the transmission characteristics.

In the conventional optical feedthrough 3, a structure in which the outer diameter is about 0.1 mm and the outer circumference of the optical fiber element wire is extremely thin is directly maintained by the epoxy adhesive and the solder to be watertight and airtight.

However, in such a structure, there is a drawback that complicated manufacturing steps such as filling by vacuum suction of an adhesive are involved in order to prevent uneven stress from being applied to the optical fiber strand during manufacturing and application of high water pressure. . Moreover, it is impossible to eliminate the non-uniform stress even in the conventional feedthrough manufactured through such a complicated and delicate process.
As a result, a slight change in optical loss due to temperature changes is inevitable. Further, if seawater pressure is applied to the feedthrough portion, the stress unevenness may be further promoted.

(3) Object of the Invention An object of the present invention is to provide a small-sized optical feedthrough excellent in pressure resistance and airtightness.

(4) Configuration of the Invention (4-1) Difference between Features of the Invention and Prior Art The present invention relates to an opening of an optical signal introduction hole of a holding member fixed to an end plate metal in a submarine optical repeater housing. , The two flat plate microlens arrays, in which the microlenses are arranged in a two-dimensional array on the flat plate substrate, are attached to the flat plate microlens array on the high-voltage side while maintaining water pressure resistance and airtightness. The optical fiber derived from the repeater circuit is formed into a two-dimensional array by joining the first optical fiber terminations, which are obtained by terminating the optical fibers of This is an optical feedthrough whose main feature is to join the terminated second optical fiber terminations, and conventionally there is no example in which the structure of the present invention is used in a portion to which high water pressure is applied.

In another example, in the optical feedthrough with the above structure, two flat plate microlens arrays are connected by a connector through a guide, and the submarine optical cable side optical fiber and the repeater circuit side optical fiber are collectively connected. The most important feature is that.

Conventionally, there is no optical feedthrough having a function of collectively connecting multiple optical fibers.

(4-2) Example FIG. 2 is a view for explaining the basic structure of the present invention, in which 10 is a holding member, 11 is a repeater circuit side optical fiber, 12 is a submarine optical cable side optical fiber, and 13 is an optical fiber. Termination part A (first optical fiber termination part), 14 is a flat plate microlens array A, 16 is a flat plate microlens array B, 17 is an optical fiber termination part B (second optical fiber termination part), 18 is adhesive, 19
Is solder, 20 is a metal coat, 21 is an O-ring, 22 is a metal C-ring, 23 is a microlens formed in flat glass, 25 is a pressing component, and 26 is a locus of signal light.

The optical feedthrough shown in FIG. 2 is usually located in a pressure resistant structure made of metal or the like and is not subject to water pressure, but there is a possibility that it will be subjected to water pressure due to flooding due to cable breakage, etc. It is necessary to prevent the infiltration of water. In FIG. 2, the left side of the end plate 5 is the high pressure side and the right side is the low pressure side.

The flat plate microlens arrays A14 and B16 are microlenses 23 in which a flat glass is provided with a three-dimensional refractive index distribution in the radius and depth directions by an ion exchange diffusion method, an electric field transfer method, or the like.
Are arranged in a two-dimensional array, and the flat plate microlens arrays A14 and B16 are joined so that the large-diameter side of each microlens 23 abuts. Further, the optical fiber terminations A13, B17 in which the end faces of the repeater circuit side optical fiber 11 and the submarine optical cable side optical fiber 12 are arranged with high precision at the focal point of the corresponding microlens 23, respectively, the flat plate microlens array A14, Stacked on B16 to form a so-called stacked optical circuit.

In this basic structure, for the watertightness and airtightness between the laminated optical circuit and the holding member 10, a metal coat 20 is applied to the outer periphery of the flat plate microlens array A14, and the metal coat 20 and the holding member 10 are sealed with solder 19. The airtightness is maintained, and the high pressure side is further sealed with an adhesive 18 to keep it watertight. It should be noted that ceramic may be applied to the material of the holding member 10, and the glass / ceramic bonding solder may be hermetically sealed.

The O-ring 21 keeps the watertightness between the holding member 10 and the end plate 5, and the metal C ring 22 keeps the airtightness on the low pressure side of the O-ring 21.

Instead of the airtight holding method using the metal C ring 22 between the holding member 10 and the end face plate 5, a contact method using a tapered cone can also be used.

As for the effect of this basic structure, the microlens 23 can be manufactured with a diameter of 0.9 mm and an interval of about the same as the diameter according to the reference (Iga et al., "Progress of microlenses", IEICE Journal 68-12, P1297). Therefore, the optical feedthrough can be dramatically reduced in size.

In addition, unlike the conventional optical feedthrough, it is not necessary to directly provide a watertight or airtight structure with an adhesive or solder to the outer circumference of a small-diameter optical fiber, and the outer circumference of the flat plate microlens array A14 is larger than the optical fiber. There is an advantage that only the watertight and airtight structure should be applied.

FIG. 3 is a diagram for explaining another basic structure of the present invention,
24 is a guide.

This basic structure allows the flat plate microlens arrays A14 and B16 in the above-mentioned laminated optical circuit to be detachable, and has a connector-type connection function via the guide 24.

Here, in order to eliminate an air layer that may generate reflected light that adversely affects the light emitting element, at the joint surface of the flat plate microlens arrays A14 and B16, a spring or the like is pressed from the left side in FIG. It is possible to employ the addition of the above, interposing a non-reflective coating film, or the like.

The effect of this basic structure is to add a connector-type optical fiber connection function to the optical feedthrough to simplify the optical connection between the submarine optical cable and the repeater circuit for construction and repair of transmission lines, and the repeater housing. It is to enable the miniaturization of the body.

(5) Effects of the Invention As described above, the flat plate microlens array optically functions as a lens array, and at the same time has mechanically excellent strength equal to that of a flat plate glass.
According to the present invention, when this is applied to an optical feed-through part which is required to have two functions different from each other in that the optical signals from a large number of fibers are collectively introduced into the repeater efficiently together with the water pressure resistant function, one element is obtained. Since this can be achieved with, there is a great effect that miniaturization and high reliability can be achieved all at once.

Also, by taking advantage of the fact that the same flat plate microlens array can be standardized and mass-produced, a connector type connection function is added between two flat plate microlens arrays via a guide, so In the submarine optical repeater housing, the fusion splicing was applied. Simplification of the optical connection between the submarine optical cable and the repeater circuit, such as the construction and repair of the transmission line, and the extra length processing part associated with the fusion splicing is unnecessary. As a result, there is an advantage that the submarine optical relay housing can be downsized.

Further, as compared with a connector in which small-diameter fibers are directly abutted to each other, the present invention has a configuration in which light from a fiber is converted into large-diameter parallel light by a microlens and is incident on a microlens on the other side. There is an advantage that a high connection efficiency can be obtained even with a collective multi-core configuration without requiring such extreme processing accuracy.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a conventional submarine optical repeater housing,
FIG. 2 is a vertical sectional view showing an example of the basic structure of the present invention, and FIG. 3 is a vertical sectional view showing another example of the present invention. 1 ... Submarine optical cable, 4 ... Repeater circuit, 5 ... End plate, 6 ... Pressure-resistant cylinder, 11 ... Optical fiber A, 12 ...
Optical fiber B, 13 ... Optical fiber termination A (first optical fiber termination), 14 ... Flat plate microlens array A,
16: Flat plate microlens array B, 17: Optical fiber termination B (second optical fiber termination), 18: Adhesive,
19 …… Solder, 20 …… Metal coat, 23 …… Microlens formed in flat glass, 24 …… Guide, 25 …… Pressing part, 26 …… Signal light trajectory.

Claims (2)

[Claims] 1. A pair of optical elements in which one or more optical fibers are respectively connected from a cable side and a repeater side to an optical signal introducing hole penetrating an end face plate of a pressure resistant cylinder of a submarine optical repeater housing, and a pair of optical elements are airtightly sealed against water pressure. The pair of optical elements is a structure in which two flat plate microlens arrays are abutted and joined from the cable side and the repeater circuit side, and the pair of optical elements are provided in the cable side flat plate microlens array. A first optical fiber termination portion is formed by arranging one or more optical fibers of the submarine optical cable so as to correspond to the positions of the individual microlenses in the array and connecting and terminating the optical fibers.
Further, in the flat plate microlens array on the repeater side, one or more optical fibers derived from the repeater circuit are arranged so as to correspond to the positions of the individual microlenses in the array. An optical feedthrough characterized in that the optical fiber terminations are joined together. 2. The optical feedthrough according to claim 1, wherein the two flat plate microlens arrays are joined by a connector type via a guide.