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  Have you ever encountered the problem that the link cannot be   up when the 1310nm optical module is transmitted on G.655 optical fiber? I encountered this kind of problem recently, and now I want to share it with you . Failure symptom Module ： 100G QSFP28 1310nm 80km optical transceiver Switch ： Cisco NCS540 Optical fiber type:   G.655, distance 50km Failure symptom:   Transmission link cannot go up. Analysis: 1.Change another switch, the link continues flap 2.Use G.652 optical fiber test in lab, Link works ok. Optical module Tx power and Rx power are in spec. That means optical transceivers performance are ok. 3.DWDM optical modules work well on G.655 link ， that means G.655 link no break.   4 . Deduce ： The optical module wavelength and fiber type don’t match Root Cause: Optical  modules with a working wavelength of 1310nm cannot use G . 655 optical fiber for long-distance transmission , G.655 Optical cable cutoff wavelength  ≤ 1480nm, work...

The Wavelength Division Multiplexing (WDM) system is a passive, optical solution for increasing the flexibility and capacity of existing fiber lines in high-speed networks. By adding more channels onto available fibers, the WDM System enables greater versatility for data communications in ring, point-to-point, and multi-point topologies for both enterprise and metro applications. Do you know about WDM system? 5 concepts provided in this blog may help you easily get it. Optical Transmission Optical transmission is the conversion of a digital stream of information to light pulses. The light pulses are generated by a laser source (LED or vessel) and transmitted over an optical fiber. The receiver converts the light pulses back to digital information. Wavelength Division Multiplexing WDM is based on the fact that optical fibers can carry more than one wavelength at the same time. The lasers are transmitting the light pulses at different wavelengths that are combined via filters to one sin...

  WDM : Wavelength division multiplexing is a technology that simultaneously transmits two or more optical  signals of different wavelengths in the same optical fiber. CWDM  : Coarse wavelength division multiplexing, generally covering wavelengths of 1270~1610nm , DFB lasers will be used , the channel spacing is relatively wide, usually 20nm , the main application, a total of 18 waves, relatively low cost, mainly used in Aggregation layer and access layer. So it can be used for our fronthaul, CWDM6 application. DWDM : dense wavelength division multiplexing, the wavelength interval will be relatively small, 0.2nm~1.2nm . The main working wavelengths are 1525nm~1565nm in C -band and 1570nm~1610nm in L- band . It focuses on long-distance transmission and is applied to the transmission network. Therefore, the low-loss C -band is selected, and EML lasers are usually used. To ensure the wavelength, they are all equipped with TEC , so the cost of the device will be relatively h...

  The coherent optical communication system modulates the signal to the optical carrier by modulating the amplitude, phase and frequency of the signal in the way of external light modulation (such as DP-QPSK) at the sending end. Compared with the traditional direct detection system, coherent detection can obtain more signal information through the beat frequency of signal light and local vibration. After the signal arrives at the receiving end, by means of high-speed digital signal processing (DSP) technology, through front-end processing such as equalization, it enters the optical mixer and the optical signal generated by the local oscillator for coherent mixing, so as to realize signal reconstruction and distortion compensation. Coherent optics is available for both 100G and 400G applications , primarily because it enables service providers to send more data over existing optical fibers, reducing the cost and complexity of network upgrades for bandwidth expansion. Main advantages...

By using standard optical modules (such as CFP and QSFP28), 100G transfers within the data center are possible. Although they are well suited for transmitting 100G traffic within racks and data centers, this can become a problem when 100G traffic needs to be transmitted over long distances (for example, long connections between different data centers (for example, over 40km)). This requires a 100G DWDM optical module. Since DWDM SFP transceivers are widely used for scaling up 10G network capacity, DWDM technology is not new to the industry. In terms of functionality, the 100G DWDM is very similar to its predecessor. However, it is often used for longer distances in a 100 gigabyte network. PAM4 and Coherence are two industry-leading solutions that offer greater bandwidth and transmission distance. When comparing 100G DWDM PAM4 to a coherent optical module, it depends on what functions the network needs and benefits from. In this article, we will analyze both options to help businesses ...

 Two important developments in fibre optic communication are the increase in transmission rate and the extension of transmission distance. As the transmission rate increases, the factors that limit the transmission distance during signal transmission become more numerous, such as chromatic dispersion, non-linear effects, polarisation mode dispersion, etc., which also affect the simultaneous increase of both. In addition there is no ideal digital channel in the actual transmission process, the signal will always have aberrations and delays in the transmission process of various media, which means error codes and jitter. To reduce the impact of these adverse factors, industry experts have proposed Forward Error Correction, or FEC (Forward Error Correction) for short. FEC is short for Forward Error Correction. Forward Error Correction is a type of error control, which refers to a technique where a signal is pre-processed according to a certain algorithm for coding before being sent i...