Shulou(Shulou.com)06/01 Report--

Ultra-long distance wavelength Division Transmission Technology

Wavelength division transmission is the most commonly used backbone network transmission mode in optical fiber networks. Wavelength division transmission is composed of CWDM/DWDM wavelength division multiplexer, EDFA optical fiber amplifier and DCM dispersion compensator, so wavelength division transmission is systematic. Today I am here to share the ultra-long distance wavelength division transmission technology.

I. types and application environment of ultra-long distance transmission

In recent years, wavelength division multiplexing technology is mainly developing in the direction of ultra-long distance and large-capacity transmission. in view of the market demand and network trend of ultra-long-distance transmission, this paper will focus on long-distance transmission and discuss the solution of ultra-long-distance transmission.

Ultra-long distance transmission includes multi-span (amplified) segment long-distance non-electric relay transmission and single-span (amplified) segment transmission. From the point of view of morphological characteristics, the former usually refers to the point-to-point transmission of 1000km~3000km without photoelectric conversion, while the latter refers to the passive amplification or relay-free point-to-point transmission of 100km~300km, as shown in figure 1. From the point of view of technical implementation, multi-span long-distance non-electric relay transmission needs to solve a series of problems, such as optical signal-to-noise ratio (OSNR), dispersion (CD), polarization mode dispersion (PMD), nonlinear effect (NL) and power equalization, while the problem of single-span transmission is relatively less, generally focusing on OSNR and nonlinear effect (NL). From the point of view of network application, the former can reduce the number of electric relay contacts up and down without service and greatly reduce the maintenance workload from the point of view of network application; the latter is mainly used in areas where active equipment or inconvenient maintenance can not be set up due to natural obstacles, such as between islands, deserts, uninhabited areas and so on.

Second, the related technology of ultra-long distance transmission

Ultra-long distance transmission is limited by physical obstacles such as dispersion effect and nonlinear effect. In order to complete the ultra-long-distance transmission, the corresponding technology must be adopted in both the terminal and the line.

1. Physical limitations of long-distance transmission

The physical obstacles encountered in optical signal transmission in optical fiber include nonlinear effect (NL), dispersion effect (CD), polarization mode dispersion (PMD) and optical signal-to-noise ratio (OSNR) limitation. Among them, the nonlinear effects include self-phase modulation (SPM), cross-phase modulation (XPM), four-wave mixing (FWM), stimulated Raman (SRS) and stimulated Brillouin (SBS) effects.

The dispersion effect (CD) can be overcome by increasing the dispersion tolerance of the terminal transmitting unit, line dispersion compensation and post-compensation at the receiver. However, there is no good commercial compensation for polarization mode dispersion (PMD), so we can only use optical fiber with good polarization mode dispersion (PMD) index (less than 0.1ps/km1/2) to achieve long-distance transmission. The limitation of optical signal-to-noise ratio (OSNR) can be solved by reducing the OSNR threshold of the transmitting unit.

The nonlinear effect that affects the long-distance transmission performance is mainly self-phase modulation (SPM), while the effect of self-phase modulation (SPM) is reflected by the interaction with fiber dispersion effect (CD), that is, the so-called dispersion pattern problem. As shown in figure 3, the change of the dispersion pattern is related to the transmission distance. With the extension of the transmission distance, the residual dispersion curve moves to the positive dispersion direction, and the dispersion window narrows at the same time.

Designer: Shenzhen Guanglu online Technology Co., Ltd.

Designer: Zhou Danyang

Technical heat type: 18617148030

Customer QQ:122 818 363

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.