JPS582B2 - Feedthrough for optical submarine repeaters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feedthrough of an optical submarine repeater constituting a long-distance optical fiber submarine cable in the field of optical communications using low-loss optical fibers.

Optical submarine repeaters are installed several thousand meters deep in the ocean, so they are exposed to seawater pressure of several hundred atmospheres.

For this reason, the optical circuits and electrical circuits of the optical submarine repeater are housed in a high-pressure resistant container made of a material that is highly resistant to seawater corrosion.

The optical or electrical circuit inside the pressure vessel and the strands of the optical fiber submarine cable are connected through a feedthrough attached to, for example, the lid of the pressure vessel.

The pressure inside the pressure vessel is usually 1 to 2 atmospheres, and the pressure difference between the inside and outside of the pressure vessel is very large.

For this reason, the feedthrough is required to have a structure that can withstand high water pressure while maintaining a high degree of airtightness.

The present invention provides a feedthrough for an optical submarine repeater that transmits and receives transmission signals between an optical circuit inside a pressure vessel and an external optical fiber cable through a lens made of a glass-based material attached to, for example, the lid of the pressure vessel. .

The present invention will be described in detail below using the drawings.

An embodiment of the invention is shown in FIG.

1 in FIG. 1 shows a lid of a pressure vessel, and a lens 3 is attached to a hole in a part or parts of the lid.

Here, a focusing lens with a tapered outer periphery is shown.

Reference numeral 2 denotes an optical fiber wire disposed on the optical axis of the lens, and couples light from the light emitting element 4 to the optical fiber wire 2 through the lens 3.

Here, 6 is a liquid or jelly-like substance filled between the lens and the end face of the optical fiber, and for example, a matching oil having a refractive index close to that of glass, such as glycerin or liquid paraffin, is used.

This matching oil is protected by a cover made of rubber, polyethylene, etc. to prevent it from flowing out.

Reference numeral 5 in FIG. 1 is a support for dissipating the heat of the light emitting element 4 to the pressure vessel, and a material such as beryllia magnetic material having good insulation and thermal conductivity is used.

Between the lens 3 and the lid 1 of the pressure vessel, there is a material, for example, for correcting the difference in coefficient of thermal expansion between the glass and the material used for the pressure vessel and maintaining the adhesion between the lens 3 and the lid 1. Use adhesive, etc.

In FIG. 1, the right side of the lid 1 of the pressure vessel shows the outside of the container, and the left side shows the inside.

Seawater pressure of several tens of atmospheres is applied to the lens 3 through the liquid or jelly-like substance 6.

The lens 3 has a tapered shape, and the more external pressure is applied, the better the adhesion between the lid 1 and the lens 30 becomes.

The lens 3 is made of sufficiently thick glass to withstand high water pressure.

FIG. 2 also shows an embodiment of the present invention, in which a glass plate 8 and a convex lens 3 are combined in place of the condensing lens shown in FIG.

As described above, a combination lens can also be used as the lens section incorporated into the pressure vessel.

The embodiment of FIG. 3 shows a case where the optical fiber submarine cable has a different structure.

In other words, a case is shown in which the optical fiber is protected by a high-pressure resistant pipe 7.

Even if the optical fiber 2 is inserted into the high-pressure-resistant pipe 7, it is necessary to prevent seawater from entering the repeater in the unlikely event that a cable failure occurs, and measures for high-pressure resistance and airtightness are shown in Figure 1.
, it is necessary to think in exactly the same way as in Figure 2.

Although the embodiments shown in FIGS. 1 to 3 are those in which a light emitting element is disposed within a pressure vessel, the same can be considered even when a light receiving element is disposed in place of the light emitting element.

Although FIGS. 1, 2, and 3 of the embodiments of the present invention show a view in which the feedthrough is attached to a part of a pressure vessel, it is also applicable to a structure in which the feedthrough according to the present invention is made into a unit and this unit is attached to a pressure vessel. This can be considered as an example.

In some cases, a plurality of such units may be installed.

FIG. 4A shows an optical repeater configuration in which an optical fiber is passed through a conventional feedthrough, and FIG. 4B shows an optical repeater configuration using a feedthrough according to the present invention.

In a, 9 indicates the repeater circuit, 10 indicates the pressure vessel, 11 indicates the optical fiber connection point in the pressure vessel, and 12 indicates the pressure vessel 1.
0 and the optical fiber submarine cable.

Reference numeral 13 indicates a cable anchorage portion for mechanically coupling the optical fiber submarine cable to the pressure vessel 10.

When a low-loss optical fiber is bent with a small radius of curvature, its transmission loss increases.

It is necessary to connect the optical fibers using a special connecting device, which requires extra length for this connection, and it is necessary to accommodate the connected optical fibers while maintaining as large a curvature as possible. As in a, the fiber connection requires a large space.

By using the feedthrough of the present invention, there is no need to connect optical fibers, and the above-mentioned space is unnecessary, making it possible to downsize the optical submarine repeater.

This is shown in Figure 4. The connection between the optical repeater circuit 9 and the feedthrough requires only electrical wiring since a light emitting or light receiving element is attached to the feedthrough, and the voltage handled here is at most several tens of volts, so these wirings are easy to connect and Since curvature is not a problem, it can be accommodated in a very small space.

The present invention provides the following effects.

(1) The high-pressure resistant container does not require micro-machining like optical fibers, and a lens that is larger than that of a fiber is attached, making machining easier to maintain high pressure resistance and high airtightness.

(2) When an optical fiber is passed through a feedthrough, at least four fiber connections are required per repeater, but according to the present invention, optical fiber connections due to the structure of the feedthrough are unnecessary.

The extra length of the optical fiber required to connect the optical fiber to the repeater becomes unnecessary, making it possible to downsize the pressure vessel and the cable connection section.

(3) On the outside of the pressure vessel, an optical fiber is placed on the optical axis of the lens, and a liquid or jelly-like substance with approximately the same oil contact ratio as glass is filled between the end face of the optical fiber and the lens. Seawater does not enter the fiber end face, and unnecessary reflections on the fiber or lens surface can be prevented.

(4) A light emitting element such as a laser diode can be disposed near the pressure vessel, making it easy to adopt a structure that improves the heat dissipation effect.

[Brief explanation of the drawing]

1, 2, and 3 are longitudinal sectional views showing embodiments of the present invention, FIG. 4a is a longitudinal sectional view of a repeater using a conventional feedsle, and FIG. 4b is a longitudinal sectional view of a repeater using the feedsle of the present invention. FIG. 1... Lid of pressure vessel, 2... Optical fiber wire, 3... Lens, 4... Light emitting element, 5... Support, 6...Filling substance,
1...High pressure resistant pipe, 8...Glass plate, 9...Relay circuit, 10...Pressure vessel, 11.12... Optical fiber connection point, 13...
...Cable retention section.

Claims (1)

[Claims] 1. In the feedthrough of an optical submarine repeater for optically coupling a repeating circuit housed in a pressure-resistant container of an optical submarine repeater and an optical fiber housed in a high-pressure-resistant pipe of an optical submarine cable, the pressure-resistant A part of the container is provided with a condensing lens fitted into a through hole having an inclination from the outside to the inside through an adhesive, and the optical fiber is supported by a support fixed to the pressure container and the condenser The optical axis of the optical lens is arranged to be aligned with the optical axis of the optical fiber, and the space between the condenser lens and the end face of the optical fiber is filled with a liquid or jelly-like substance having a refractive index substantially equal to the refractive index of the optical fiber. A feedthrough for an optical submarine repeater, characterized in that the high-pressure-resistant pipe is fixed to the pressure-resistant container.