SAGEM 3P@C

C.Fiber-related Knowledge

The center of an optical fiber is a glass core for optical transmission. The core is surrounded by a layer of glass envelope, whose refractive index is lower than that of the core to keep the optical fiber within the core. Out of the glass envelope is a layer of thin plastic sheath to protect the envelope. The high reliability, transmission quality and gradual adoption of new technologies in design and manufacturing make the optical fiber cables have an even wider application range.

C.1 Multi-Mode and Single-Mode Optical Fiber Cables

The optical fiber system can be divided into two categories according to the optical transmission mode: multimode and single-mode. A single-mode optical fiber cable has a very small core (4 um to 10 um) and can only transmit signals in single mode at a given wavelength. Its transmission bandwidth is wide and the transmission capacity is quite large. You can tell single-mode fiber cables from multi-mode fiber cables easily based on the size of their cores.

Multi-mode fibers can support multiple transmission modes on a given wavelength. In multi-mode transmission, different modes of optical signals are transmitted at different rates through the same fiber. This can result in phase difference, which, in turn, causes transmission distortion. And therefore, the frequency band that a multimode optical fiber can provide is restricted. Two specifications are available now for the cores of multi-mode optical fibers: 62.5mm and 50mm. In ISO/IEC 11801, both the two modes are recognized transmission media.

C.2 Wavelength range of the optical fiber

Optical wave bands adopted for optical fiber cabling: 800nm to 900nm short wave band, 1250nm to 1350nm long wave band and 1500nm to 1600nm long wave band.

In these bands, the optical fiber performs best at the central wavelength of each band. Therefore the operating wavelength of the multimode optical fiber is 850nm or 1300nm and the operating wavelength of the single mode optical fiber is 1310nm or 1550nm.

C.3 Optical Fiber Connector

The optical connector, a demountable device, is defined by International Telecommunication Union (ITU) as fiber optic passive component that connects stably but not permanently two or more optical fibers. In March 1992, Study Group VI of CCITT (Consultative Committee for International Telegraphy and Telephony) formally adopted the definition. The optical connector is an indispensable passive device in optical communication system and makes the demountable connection of optical channels possible. The optical connector has many kinds. For example:

„FC optical connector, round and threaded

„ST optical connector, plug-in and round-head

„SC optical connector, square-head

„MT-RJ square optical connector capable of both receiving and sending

The following is the appearance of the SC connector and MT-RJ connector, as shown in Figure C-1 and C-2:

Figure C-1 Appearance of the SC connector

3P@C Installation Manual

Reproduction and communication in any form prohibited without the written permission of SAGEM SA