Download Fiber Optic Coupler 1

Very Small (VS) Fiber Optic
Coupler Assembly
Description
The Very Small (VS) Fiber Optic Coupler assembly is a completely new approach to coupling optical fibers. Developed by
engineers at the Kansas City Plant, the coupler provides multifunction capability—tests for fiber integrity can be conducted
before using the optical fibers as intended within the larger
sensing system. Yet, this small assembly requires less than 2/
10ths of 1 percent of the space needed for a typical commercial fiber coupler.
Using small commercial connectors in a unique configuration measurably improves existing
fiber optic coupler technology. The illustration shows that light sent from a fiber moves through
the VS Fiber Optic Coupler and is returned from a coating at the end of the second fiber. The light
then passes into a third fiber, where it is measured to determine the integrity of the extended fiber
sensing system or to perform the actual sensing activity. A variation of the fiber coupler assembly uses
small segments of lenses to increase coupler efficiency.
Background
The new VS Optical Fiber Coupler was developed to replace the large commercial couplers used in a highdemand, extended fiber integrity testing system. This system is a critical component of the High Explosive
Radio Telemetry (HERT) application. The HERT is part of the Kansas City Plant’s Advanced Telemetry Project,
which is working to revolutionize telemetry flight test instrumentation for the most complex and demanding
applications, specifically weapon flight tests.
These flight tests have dynamic requirements that demand more performance from smaller physical packages.
Fiber integrity testing must occur before running actual telemetry flight tests, but Kansas City Plant engineers
found that existing commercial fiber optic couplers were too large for the space available in the HERT system.
Conventional coupler fabrication begins by wrapping optical fibers together. These are fused and stretched to
make the coupler. Once in place, the conventional assembly is fixed—no additional optical fibers can be added to
it—and the coupler area is large, up to 3” by 0.25”.
Advantages
To meet the HERT technical requirements, Kansas City Plant engineers have approached optical fiber coupling in
a new way. Changes to the fabrication process produces a coupler small enough to fit into a space 0.20” by 0.08”
by 0.1”, making it ideal for applications with significant space constraints. Yet, the efficiency of the VS Optical Fiber
Coupler is comparable to that of its much larger, commercial counterparts. Using a simple spherical lens at the coupling joint reduces transmission loss from 93 percent to 75 percent.
Design improvements make the new coupler assembly expandable. Using standard fibers and commercially available ferrules, the passively aligned fiber coupler could consist of up to eight, three-fiber coupling units. Thus, assembly of the VS Optical Fiber Coupler is straightforward, adaptable to volume production, cost efficient, and flexible in
configuration. It is also easy to customize coupler assemblies for specific applications.
Applications
With its important technical improvements, the VS Optical Fiber Coupler contributes to the miniaturization of end products. Optical
fiber sensing systems are used to detect a wide range of physical, chemical, and biological properties. The small size of this new coupler
assembly makes it possible to place it inside common packages that house small detectors and light sources, such as LEDs or vertical
cavity side emitting lasers. Therefore, the VS Optical Fiber Coupler holds promise for applications where device size is crucial, such as:
➣ Biological or chemical detection;
➣ Small, unmanned surveillance drones;
➣ Satellites
Satellites and space vehicles;
➣ Biomedical and patient monitoring devices, such as cardiovascular monitoring systems;
➣ Data communication.