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OTN Composition in DWDM Network

Date: 2021-04-01 06:39:25 From: C-light Onclick:

 DWDM usually have two forms of application:
1. Integrated DWDM
Integrated DWDM systems do not use wavelength conversion technology, which requires multiplexing terminal optical signals wavelength. According to the specification of the DWDM system, different multiplexing terminal devices send different conformance ITU-T the suggested wavelength, so that they can occupy different channels when connected to the receiver in order to complete the wave.
Integration scenario: less than 10%, promoted by the Cisco, but not widely used. The key problem is that the integrated system puts the conversion ability of color light on the router. The signal service quality of each channel can not be monitored on the wave division equipment. In case of failure, location is difficult, location time is long, and it is easy to be wrangling between different departments within the operator and the operator.
2. Open DWDM
An open DWDM system is characterized by no special requirements for multiplexing terminal optical interfaces, provided that these interfaces to meet ITU-T recommended optical interface standards. DWDM system uses wavelength conversion technology to convert optical signals of multiplexed terminals into optical signals of specified wavelengths and different terminal devices converted to different wavelengths consistent with the ITU-T's recommendations, followed by a combined wave watermark.
The main features of the open system are: the client side outputs the gray light signal, and the gray light signal is converted to the color light signal of the wave division by the OTU on the wave division equipment. For 80 wave equipment, 80 pairs of OTU units are generally needed. This open system is the most commonly used application scenario, accounting for more than 90% of the total. It is convenient for operators to bid separately for different kinds of equipment, and can quickly locate the fault when the network fails.
To the supplier, because the wavelength expansion needs to purchase OTU, is also a very popular operation scenario for the supplier, because the future expansion is basically on the OTU.
WDM System composition
The overall structure of N wavelength multiplexing WDM system is mainly composed of transmitting and receiving optical multiplexing terminals (OMT). The unit is composed of a developed (ILA) unit of the relay line if it is in a constituent mode. There are:
1. Optical wavelength conversion unit (OTU);
Optical wavelength conversion unit (OTU) converts non-standard wavelengths to ITU-T standard specified wavelength. In system the application of an optical/electric/optical (0/ E/0) transformation, i.e. PIN or APD connection with a photodiode. The received optical signal is converted into an electrical signal, which then carries on the standard wavelength laser modulation to obtain a new optical wavelength signal.
2. Wavelength division multiplexer: wavelength division / combiner (ODU/OMU);
The wavelength division multiplexer can be divided into the starting end of the photosynthetic filter for transmission system end is a device with multiple input ports and one output port, each of which is transmitted. The input port inputs a pre-selected wavelength optical signal, and the input light wave of different wavelengths is transmitted by the same-transport out port output. The optical splitter is used at the receiving end of the transmission system, in contrast to the photosynthetic filter, it has one input port and multiple output ports, which classify multiple different wavelength signals.
3. Optical amplifier (BA/LA/PA);
The optical amplifier can not only amplify the optical signal directly, but also has real-time, high gain and high gain, wideband, on-line, low noise and low loss all-optical amplifier, is a new generation optical fiber communication system essential key devices.

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Optical fiber amplifier (Optical Fiber Amplifier, abbreviated OFA) refers to a new type of all-optical amplifier used in optical fiber communication lines to achieve signal amplification. According to its position and function in the optical fiber line, it is generally divided into three types: relay amplification, pre-amplification and power amplification. Compared with the traditional semiconductor laser amplifier (SOA), OFA does not need to go through complicated processes such as photoelectric conversion, electro-optical conversion and signal regeneration. It can directly perform all-optical amplification of the signal. It has good "transparency" and is especially suitable for long distances, relay amplification of optical communication. It can be said that OFA has laid a technical foundation for the realization of all-optical communication. 
At present, erbium-doped fiber amplifiers are the main fiber amplifier in practice (EDFA), Erbium-doped fiber amplifier is widely used in long distance and large capacity because of its superior performance In the optical fiber communication system.
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4. Optical monitoring channel/path (OSC);
An optical monitoring channel is set up for the monitoring of WDM optical transmission systems. ITU-T recommendations using 1510 nm wavelength with capacity of 2 Mbit/s. High reception sensitivity (excellent) at low rate at -50 dBm) can still work properly. But it has to be light up before EDFA, but on light path after EDFA.
According to the needs of the project, different application forms can be selected. In practice Open DWDM and integrated DWDM can be mixed.