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Wavelength measurement technology of dense optical wavelength division multiplexing system

the information explosion in the information age leads to the explosion of communication bandwidth demand or communication network capacity. For example, recently, the business volume of the backbone in North America has doubled in about months, reaching the so-called "speed of light economy", which is times faster than Moore's law for the performance development of microelectronic chips (doubling in about 18 months), and this development momentum has not decreased so far. In the face of this development trend, various developed communication countries are actively studying and designing new broadband networks, such as sustainable development network Cun, next generation network NGN, new public NPN, integrated UN, etc. but the physical layer of its basic transmission medium is the optical transmission OTN of dense optical wavelength division multiplexing (DWDM). Otherwise, it is impossible to provide huge communication bandwidth, highly reliable transmission performance, sufficient service carrying capacity and low cost to ensure the sustainable development of the network and support the transmission requirements of any service signal at present and in the future. Dense optical wavelength division multiplexing (DWDM) system DWDM system is mainly composed of optical automobile front axle fatigue life test steps: wave combiner, optical wavelength divider and erbium-doped fiber amplifier (EDFA). The function of EDFA is to radiate energy into a section of erbium-doped fiber by a high-energy optical pump source lower than the signal wavelength. When the light waves carrying the net load propagate together through this section of fiber, the optical energy transfer is completed, so that the net load signals carried by each light wave within the M wavelength range are amplified, making up for the energy loss of the optical fiber line. In this way, when EDFA is used to replace the relay equipment in the traditional optical communication link, the transmission capacity can be directly increased by increasing the number of wavelengths at the least cost, which greatly simplifies the structure and design of the entire optical communication system and facilitates construction and maintenance. When EDFA is applied in DWDM system, it can be divided into three types: power amplifier or post amplifier (BA), pre amplifier or pre amplifier (PA) and line amplifier (LA). However, in order to simplify, some companies try to reduce the variety of equipment and unify it as OA to facilitate maintenance. At present, the data rate of each wavelength of commercial DWDM system is 2.5Gbps, or 10Gbps, and the number of wavelengths is 4, 8, 16, 32, etc; DWDM systems with 40, 80 or even 132 wavelengths have been produced. There are two types of configurations commonly used. One is to set the wavelength converter OTU in front of the optical combiner and behind the optical splitter. This type of configuration is open. The optical transmission and optical receiver module of any manufacturer in the existing 1310nm and 1550nm wavelength range can be used; The wavelength converter converts these non-standard optical wavelength signals to the standard optical wavelength signals specified in the 1550nm window for transmission in the DWDM system. Ciena company in the United States and Pirelli company in Europe adopt this kind of configuration. They are the companies that produce optical devices. Generally, the optical splitter and combiner produced by them have better optical performance parameters. For example, the channel wavelength interval adopted by ciena company is 0.8nm, corresponding to the bandwidth of 100GHz, at 1545 16 optical channels or optical paths are provided in the 4nm wavelength range. However, they do not have SDH transmission equipment, so they cannot be considered uniformly in terms of system configuration and network management. This kind of configuration has the advantages of flexible application and strong universality, but has the disadvantages of adding wavelength converters and high cost. The other type of configuration is to integrate the wavelength division multiplexing and demultiplexing parts with the transmission system products without wavelength converter. This type of configuration is integrated or integrated, which simplifies the system structure, reduces the cost, and facilitates the management and operation of SDH transmission equipment and DWDM equipment in the system to a great extent, which prevents the experimental machine from performing normal experiments on the same tube platform in different environments. Manufacturers of such configurations, such as lucent, Siemens, nort el, etc., are SDH transmission system equipment suppliers. They are qualified to do so. They are within ± 0.5% of the set value of 4; × 2.5g32bpsdwdm system design × For 10Gbps rate compatibility, consider adding 8 wavelengths, 16 wavelengths, 40 wavelengths and 80 wavelengths, as well as the mixed application of 2.5Gbps and 10Gbps, to ensure that the system continues to expand the capacity of the two clamps to separate and stretch the sample at a certain speed, so as to make a smooth transition without affecting the communication service. Of course, they also provide open configuration, or open sending and receiving DWDM system equipment. Since the bandwidth of the early commercial EDFA was flat in nm, the multiplexed optical wavelength of the early DWDM system was mostly around 1550nm. Later, the gain spectral width of the actual EDFA was 35nM, about 4.2thz, in which the gain fluctuation was less than 1dB, and the spectral width was between nm. If the wavelength interval was 1.6nm (corresponding to 200ghz), the synchronous amplification of 8 or even 16 wavelengths could be achieved at least; At a wavelength interval of 0.8nm (corresponding to 100GHz), DWDM systems with at least 16 wavelengths or even 32 wavelengths can be realized. In addition, EDFA has the advantages of high gain of about 40dB, high output power greater than 100MW, and low noise value of DB, which greatly promotes the rapid development of DWDM systems. Just like the electric amplifier, the optical amplifier not only amplifies the optical signal, but also introduces noise. It is produced by the spontaneousemission of photons. This kind of noise and optical signal are amplified together in the optical amplifier and accumulated step by step to form an interference signal, that is, the well-known amplified spontaneous emission (ASE) interference signal. The power of this ASE interference signal accumulated by multiple optical amplifiers will be as large as MW, and its spectrum distribution corresponds to the wavelength gain spectrum. This is the main reason why the optical digital signal processing must be completed by photoelectric conversion after several Ola amplification, taking out the electrical signals of each wavelength optical path for timing, shaping and regeneration (3R), which determines the maximum distance or the maximum number of optical relay segments of the electrical relay segment or multiplexing segment. Of course, other factors, such as the allowable total dispersion value, also determine the maximum distance of the electrical relay section. This is determined by which factor is the most stringent when the system is designed for optical power budget. The testing requirements of DWDM system are very different between multi wavelength dense optical wavelength division multiplexing system based on SDH terminal equipment and single wavelength SDH system. First of all, the accurate wavelength measurement of single wavelength optical communication system is not important. Just use an ordinary optical power meter to measure the optical power value to judge whether the optical system is normal. Set the optical power meter to a specific wavelength value, such as 1310nm or 1550nm, which is only used as

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