Introduction to optical fiber access technology

Optical fiber access technology is still a mainstream access technology, and many different optical fiber access technologies have emerged. The emergence of these technologies also makes up for the shortcomings of many access technologies, it also gives users more convenience.

1. Optical Fiber for Transmission

The Application of Optical Fiber Technology in transmission systems is first achieved through various optical networks. Up to now, the topology of various optical fiber transmission networks can be divided into three categories: Star, bus, and ring. In terms of the layered network model, the network can be divided into several layers from top to bottom, and each layer can be divided into several subnets. That is to say, networks and networks composed of extremely high transmission systems in each switch center can be further divided into several smaller subnets, so that the entire digital network can effectively communicate with services, full Digital Integrated Service Digital Network ISON) is the overall goal of the communication network. With the popularization of ADSL and CATV and the increasing capacity of Metro access systems, the expansion of trunk backbone networks requires different types of optical fiber to take on the important responsibilities of transmission.

2. Dispersion Compensation Optical Fiber DCF)

Fiber dispersion can increase the pulse width and cause the error code. This is a problem that must be avoided in the communication network and also a problem that needs to be solved in the long-distance transmission system. In general, the dispersion of optical fibers includes material dispersion and waveguide structure dispersion. The dispersion of materials depends on the dispersion of silica masterbatch and doping agents of optical fibers, waveguide Dispersion is usually a kind of pattern in which the effective refractive index changes with the wavelength. Dispersion Compensation Optical fiber is a technology used in transmission systems to solve dispersion management. USF (non-dispersion displacement optical fiber) is dominated by positive material dispersion. It is combined with small Waveguide Dispersion to produce zero dispersion near 1310nm. The dispersion-displacement Optical Fiber DSF) and non-zero dispersion-displacement Optical Fiber NZDSF are based on technical means, and the refractive index distribution of the optical fiber is designed to generate Waveguide Dispersion compared with the material dispersion, after the addition of material dispersion and Waveguide Dispersion, the zero dispersion wavelength of DSF is moved to the vicinity of 1550nm. The 1550nm wavelength is the most widely used wavelength in today's communication networks. In the submarine optical fiber transmission system, the two optical fibers with normal and negative dispersion are combined to form a Transmission System for Dispersion management. As the distance of the transmission system increases and the capacity increases, a large number of WDM and DWDM systems are put into use. In these systems, in order to compensate for dispersion, a dual-package layer and three-package layer DCF which can work in the C and L bands are developed. The dispersion value of SMF that can be used for Dispersion Compensation in the C band is 60 ~ 65 Ps/nm/km, with a valid Apff area of 23 ~ 28m2, the loss is 0.225 ~ 0.265 dB/km.

3. Optical Fiber for amplification

Doped with Rare Earth Elements in the core layer of the Z optical fiber can be used as an amplified optical fiber, for example, EDF and TOF. The amplified optical fiber has good integration performance with the traditional Z optical fiber, and has many advantages such as high output, wide band, and low noise. Fiber Amplifiers, such as EDFA, made from amplified optical fibers, are the most widely used key devices in today's transmission systems. The extended bandwidth of EDF has been increased from 1530 to in the C-band ~ 1560nm) expanded to L-band 1570 ~ Up to nm bandwidth. The latest research results show that EDF can also be in the sband 1460 ~ At 1530nm), an induction Raman optical fiber amplifier has been manufactured and amplified at the S band.

For L-band 1530 ~ Nm) amplified optical fiber, has been developed in the field of high output dual-packet layer optical fiber. Among them, the first package layer multi-mode transmission pump light, in the single-mode package layer of the fiber core transmission signal light and doped with nail Yd) as a photosensitive agent to increase the absorption coefficient.

In order to solve the non-linearity of optical fiber, EYDF optical fiber is made by co-doping rare earth elements such as Yb or La. This type of optical fiber has almost no FWM. This is because the distance between Er ions is increased after Yb ions and Er ions are assembled, and the extinction of concentration caused by excessive concentration of Ev ions is solved, at the same time, the doping of Er ions is increased, the gain coefficient is increased, and the non-linearity is reduced.

For L-band 1570 ~ 1610nm) amplified optical fiber, which has been reported to be expanded to the L-band EDF using a C-band EDF with a length of 1/3 short size EDF. An L-Band Three-Level Optical Fiber Amplifier with 40 Gbit/s high-speed transmission and zero total dispersion is successfully created. The first section of the amplifier is the conventional EDF with negative dispersion, and the second and third sections of the wavelength dispersion value is a positive short size EDF.

For sband 1460 ~ With 1530nm) amplified optical fiber, Japan's NEC adopts dual-wavelength pump GS-TD FA for long-distance transmission test of 10.92 Tb/S, and achieves a conversion rate of 29% by using 1440nm and 1560nm dual-wavelength laser LD; NTT adopts single-wave and 1440nm dual-channel pumped lasers to achieve a conversion rate of 42% and the doping concentration of 6000ppm). Alcatei adopts a multi-wave Raman laser of 1240 and 1400nm to achieve a conversion rate of 48%, at the same time, the use of 800nm titandiamond laser and 1400 multi-level Raman laser dual-wavelength pump to achieve a conversion rate of 50%, the latest report Japanese Xu nitrate company also proposed to Bi) the S-band pump amplification scheme of oxide glass as matrix material. In short, the main technical topic to be solved is how to reduce the amount of noise and increase the quantum efficiency.

1. New technologies of ADSL Access networks are emerging
2. Perfect solution for ADSL Broadband Access Technology
3. Simple and practical Wireless Access Network Solution
4. Maximize the technical efficiency of Remote Access
5. ADSL access network speed