Sagem 4450E - Manual (Page 196)

SAGEM 3P@C
3P@C Installation Manual
Reproduction and communication in any form prohibited without the written permission of SAGEM SA
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: multi-
mode 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 multi-
mode 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