At present, several typical methods in optical fiber communication applications include:
1. WDM: Wavelength division multiplexing technology – suitable for long-distance, large-capacity signal bearers, including CWDM, DWDM, for communication network trunk systems, currently China Telecom has 40G *80 wave application
2, SDH: Synchronous digital series – providing 2M PDH to 10G SDH signal bearer, mainly used for signal bearer at all levels of the communication network; extended technologies include MSTP (MSAP), ASON, IP evolution The direction is PTN
3, PON: Passive optical network – applied at the access level, solves the broadband access network, the mainstream technology is EPON and GPON, FTTx regards its specific implementation mode
4, “fiber direct drive” : (non-standard concept ) Apply point-to-point access to solve the problem that electrical signals cannot be transmitted over long distances, typically including photoelectric converters, optical cats, etc.
Direct fiber drive: The routers are connected by fiber, and the routers are centralized, scheduled, and transmitted.
Single Mode Fiber: The center glass core is very thin (the core diameter is generally 9 or 10 μm) and can only transmit one mode of light. Therefore, the inter-mode dispersion is small, suitable for remote communication, but there are also material dispersion and waveguide dispersion, so that single-mode fiber has high requirements on the spectral width and stability of the light source, that is, the spectral width is narrow and stable. It’s better. Later, it was found that at the wavelength of 1.31 μm, the material dispersion and waveguide dispersion of the single-mode fiber was positive and negative, and the sizes were exactly equal. Thus, the 1.31μm wavelength region becomes an ideal working window for fiber-optic communication. It is also the main working band of the practical fiber-optic communication system. The main parameters of the conventional single-mode fiber are 1.31μm. The main parameters of the ITU-T in the G652 are recommended by the International Telecommunication Union. Certainly, this fiber is also called G652 fiber.
A single-mode fiber does not have only one wavelength. It can only use one wavelength in the same direction. The uplink and downlink are different wavelengths, but it is impossible to use different wavelengths at the same time (or at the same time).
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