One of the most overlooked aspects of telecommunications is the physical junction between two optical fibers. Due to the directional and polarized nature of multiplexed light, great care must be taken when coupling between two separate optical fibers. A subpar fusion splice or the use of cheap connectors can lead to undue loss of optical power and distortion.
Splicing an electrical wire is a relatively simple job. Many of us have done this personally with just a razor blade and electrical tape, or a wire stripper and crimp connectors. However, the transmission of electricity is infinitely simpler than the transmission of multiplexed light waves used in modern telecom systems.
Great care must be taken when cutting, fusing and testing the connections. Cutters designed for this purpose allow perfectly perpendicular cuts, which are essential for low-loss coupling. Any air gap between the two fibers will increase Fresnel refraction along the interface because air has a different index of refraction than silica fibers. Any air gap will cause optical return loss through reflection at this interface and additional power loss through refraction. To ensure perfect transmission, professional technicians will often examine the cut with a microscope (100X-200X) for dust or chips before fusion.
The splice with the least optical losses is created through fusion splicing. This is a method that uses heat to covalently bond the silicon and oxygen atoms in adjoining segments of fiber. The best way to get the silica fibers around their melting points of 2,912°F is to use a tiny high-voltage arc of electricity. This process leads to a molecular coupling and transmission power losses of only 0.05 to 0.2 dBm. The lower end of this spectrum is achieved by aligning the two fibers optically (by sending laser light through the fibers) and by manipulating the connection until the minimum loss is measured.
The termination of fibers is an art in its own right. The fiber is stripped, glued and inserted into the back of the connector. After the epoxy is dried and the ferrule crimped, the tip of the protruding optical fiber is cut, deburred and polished with progressively finer microabrasive pads. This leads to a very smooth and slightly convex tip, which allows the best possible exchange of light between the fiber and the internal semiconductor electronics. A well-spliced connector has a power loss of about 0.2 to 1 dBm. Newer and quicker connectors that don't rely on epoxy and polishing are available, but they are more expensive with higher optical losses.
High-speed telecommunications relies heavily on the precision of field technicians. The lowest power losses can be achieved by an experienced team dedicated to creating the highest fidelity connections.
To learn more about fiber optics and structured cabling, contact TelWare at 1-800-637-3148 or firstname.lastname@example.org. TelWare is a national leader in the installation of voice, video, data and unified communications solutions. TelWare is an authorized Avaya, Star2Star, SimpleWAN and 3CX dealer.