Configuration elements as well as proper selection of wavelength to be utilized should be considered carefully when designing the optical transmission system.
The range of wavelength currently used widely is about 1.25µm-1.3µm. The wavelength having a range of 1.5µm-1.6µm is currently under development. In the band of 0.8µm wavelength, loss of optical fiber is greater than that of long wavelength range. GaAlAs(light source) and Si (light receiving element) being developed early, was commercialized in 1970s. On the other hand, in the band of 1.8µm wavelength, the loss of optical fiber is the lowest and since the material distribution of abastoes optical fiber is almost 0-is ideal for sending high speed and wideband information to farther places. The wavelength in the range of 1.5µm experiences the lowest loss. Accordingly, with successfully developing and commercializing a photo element for this range, a system with a regeneration distance of longer than 100km will be used. In actual applications, even if the optical fiber experiences low loss of 0.2dB/km, low loss characteristics is not utilized fully because of the increase in connection loss and material distribution.
The transmission speed of digital system and the transmission bandwidth of analog system are restricted by the type of optical fibers and light emitting elements used.
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