Broad bandwidth optical fibers, jacketed optical fibers and opti

Details Broad bandwidth optical fibers, jacketed optical fibers and opti Broad bandwidth optical fibers, jacketed optical fibers and opti

1996-05-08

1997-07-01

Lee, John D.

Optical waveguides

Optical fiber waveguide with cladding

With graded index core or cladding

385145, 385128, G02B 6132, G02B 616

Patent

active

056446705

DESCRIPTION:

BRIEF SUMMARY
TECHNOLOGICAL AREA

This invention relates to graded index broadband optical fibers suitable for light transmission in various data communication areas involving voice, image, text, etc. because of their high-speed signal transmission capabilities, as well as secondary-coated optical fiber units and optical fiber cords based on them.


CONVENTIONAL TECHNOLOGIES

Among telecommunications optical fibers designed for the establishment of high-speed, high-capacity data links are quartz multi-mode optical fibers and quartz single-mode optical fibers which use quartz glass in their cores and cladding, and their technical requirements are laid out in JIS (Japanese Industrial Standards) C 6832, 6835 and 6831. Jacketed optical fiber units based on them incorporate an optical fiber or fibers, each provided with a primary coating, made of an ultraviolet (UV) cured resin or silicone resin and surrounding the quartz glass claddings, and a secondary coating, made of polyamide resin or the like and surrounding it/them.
Apart from quartz single-mode optical fibers, only graded index quartz multi-mode optical fibers (hereinafter referred to as GI quartz optical fibers) are capable of high-speed optical signal transmission (e.g. those with a bandwidth of 200 MHz.times.km or more). With GI quartz optical fibers, the refractive index profile of the core is optimized to minimize mode dispersion, which is a transmission bandwidth limiting factor, with the core diameter normally set in the 50-100 .mu.m range (particularly 50 .mu.m and 62.5 .mu.m).
Since the cores and claddings of GI quartz optical fibers are made of quartz glass, attaching a crimp-type connector by crimping after the removal of the primary and secondary coatings, which are made of polymers, causes them to crack or chip. Also, if a crimp-type connector is attached by crimping without removing the primary and secondary coatings, axial misalignment results, causing a large optical connection loss, which makes this method practically unusable.
Conventionally, therefore, it was necessary to use an adhesive-type connector, in which the fiber is fixed at its center by means of a thermosetting, UV-cured, thermoplastic or two-part adhesive agent after removing the primary and secondary coatings, made of polymers, to avoid the above problems.
However, adhesive-type connectors take a long time to install and are therefore undesirable in terms of cost and labor.
In this respect, crimp-type connectors are advantageous as they can be installed far more easily and quickly than adhesive-type connectors, and are widely used for polymer cladding quartz optical fibers (hereinafter referred to as PCFs) and plastic optical fibers.
A PCF consists of a quartz glass core and plastic cladding, with a large core diameter, usually 200 .mu.m or more, and has a narrow bandwidth compared to a GI quartz optical fiber, which has a quartz glass cladding. Although a version of PCF with a graded index core (i.e. GI fiber) exists (Japanese Laid-open Patent No. 3-245108 (1991), its bandwidth, which is only in the 60-90 MHz*km range, is inadequate.
Although a PCF is advantageous in that it allows the use of a crimp-type connector, it is associated with the problem of inadequate transmission distance in, for example, applications involving FDDI (Fiber Distributed Data Interface), an optical fiber based computer communication standard, due to its narrow bandwidth.
Also, a method of utilizing a crimp-type connector for a quartz optical fiber by providing a cover made of a rigid polymer called thermoplastic fluoroacrylate resin, which has a Shore hardness of D 65 or more, over the quartz fiber cladding has been proposed in the Japanese Laid-open Patent No. 2-151821 (1990).
Although this method is fairly effective for optical fibers with a cladding diameter of 125 .mu.m and a rigid polymer covering layer diameter of 140 .mu.m or more, problems remain in that such large diameters make connection with existing GI quartz optical fibers, which conform to a standard optical fiber diameter of 125.+-.3 .mu.m, a

REFERENCES:
patent: 4482204 (1984-11-01), Blyer, Jr. et al.
patent: 4690503 (1987-09-01), Janssen et al.
patent: 4877306 (1989-10-01), Kar
patent: 5062685 (1991-11-01), Cain et al.
patent: 5123076 (1992-06-01), Nishimoto et al.

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