In recent years, the development of science and technology to speed up the pace, over six cable manufacturers integrated wiring communication industry is also booming, erbium-doped fiber amplifier (EDFA), distributed fiber Raman amplifier (DRFA), semiconductor optical amplifier (SOA), optical time division multiplexing (OTDM) technology and dense wavelength division multiplexing (DWDM) technology a wide range of applications. Optical fiber communication technology is constantly developing in the direction of higher transmission rate and larger capacity.
At present, the advanced optical fiber manufacturing technology is developing fast. Today, it can not only maintain more stable and reliable information transmission and enough redundancy, but also meet the demand of fiber communication for high broadband rate and reduce nonlinear damage. If optical fiber communication technology continues to move forward according to the present pace, it is expected to develop in all kinds of branches such as full wave fiber, multi-mode optical fiber, photonic crystal fiber and polymer optical fiber.
Full wave optical fiber
With the increasing demand for optical fiber bandwidth, the communication industry has been trying to find out the way to eliminate the “water absorption peak” with the continuous expansion of the bandwidth demand of the six types of network lines. Full wave optical fiber (All-WaveFiber) manufacturing technology production, in essence, is to eliminate as much as possible to OH ion “water absorption peak” is a specialized production technology, it makes the ordinary standard single-mode fiber in the attenuation peak near 1383nm, down to a low enough level.
The network operator’s point of view, a full wave optical fiber, we can use the coarse wavelength division multiplexing technology, the channel spacing is about 20nm, then can provide greater bandwidth for the network at the same time, the filter and the laser performance is greatly reduced, which greatly reduces the network operator’s construction cost. The emergence of full wave fiber has made the optical communication business more flexible. Because of the wide waveband that can be used for communication, we can divide the waveband of full wave fiber into different communication segments and use them separately. It is foreseeable that this full wave optical fiber will be used in the construction of the City metropolitan area network in the future.
The desire of human to pursue high-speed and broadband communication networks is endless. In the case of bandwidth demand increasing exponentially, full wave fiber is attracting more and more attention from the industry. Its many advantages have been widely accepted by the communication industry.
With the establishment of Gigabit Ethernet, Ethernet will also upgrade from Gbps to 10Gbps. The progress of communication technology has greatly promoted the development of multimode optical fiber. The central fiber core of the multimode fiber is coarser (50 or 62.5 mu m), which can transmit a variety of modes of light. The common multimode fibers are: 50/125 mu m (European standard), 62.5/125 mu m (American Standard). In recent years, the growth rate of application of multimode fiber is very fast, this is mainly because of the optical fiber communication technology will gradually shift the further development of parallel optical interconnection element application also greatly promote the rapid growth of the short-range multimode cable market, so that the multimode fiber market share continued to rise.
Photonic crystal fiber
The photonic crystal fiber (photoniccrystalfiber, PCF) was proposed by ST.J.Russell and others in 1992. The quartz fiber, the structure characteristics of PCF are uniformly arranged along the axial air hole in the middle, so from the end face of the fiber, there is a two-dimensional periodic structure, if one hole damaged and missing, there will be defects, using this defect, light can propagate in them. PCF is different from ordinary single mode fiber. Because it is made up of single quartz material with periodic arrangement of air holes, it has the name of hollow optical fiber (holeyfiber) or microstructured optical fiber (micro-structuredfiber). PCF has special dispersion and nonlinear characteristics, and will be widely used in the field of optical communication.
The striking feature of PCF is that its structure is reasonable, and it has the capability of supporting single mode transmission at all wavelengths. The so-called “endless single-mode” characteristic (endlesslysingle-mode) has been well explained in theory. This needs to meet the condition that the air hole is small enough, and the ratio of the air aperture to the distance between the holes must not be more than 0.2. The larger air hole PCF will be the same as ordinary fiber, and there will be a multimode phenomenon in the short wave length.
Another feature of PCF, a super six type network line manufacturer, is that it has a singular dispersion characteristic. Now people have successfully produced 850nm optical solitons in PCF, and the future wavelengths are expected to be reduced. In addition, some companies have developed new photonic crystal fiber, a hollow air waveguide photonic bandgap fiber “(air-guidingPhotonicBandgapFiber), the crystal fiber core is hollow, using air as a waveguide, allows the light to be in a special transmission band gap. Another is the “double clad high numerical aperture Yb fiber” (DoubleClad High NA Yb Fiber), the optical fiber can be used in fiber laser or fiber amplifier, as the fiber has a photosensitive, it can also in fiber Bragg grating inscription.
Polymer optical fiber
At present, communication backbone has realized the communication based on silica fiber. However, in the access network and fiber to the house (FTTH) project, silica fiber has encountered great difficulties. As the core of quartz fiber is very thin (6? 10 m), optical fiber coupling and interconnection are facing technical difficulties, because the alignment technology needs high precision, so the user access network for short distance, contact is a problem.
Polymer optical fiber (polymeropticalfiber, POF) because of its large core diameter (0.2? 1.5mm), so it can use inexpensive injection connector and simple, and its toughness and flexibility are good, large numerical aperture, can use laser source of cheap, low loss window in the visible region, suitable for the access network. Polymer optical fiber is the most promising transmission medium in FTTH engineering.
The polymer fiber is divided into multimode step type SI-POF and type GI-POF multimode graded two categories, due to the existence of SIPOF mode dispersion is serious, the transmission bandwidth is similar to copper wires limited within 5MHz, even in a very short distance communication can meet the communication requirements of standard FDDI, SDH, B-ISDN, and the refractive index of the GIPOF fiber the core rate distribution is a parabola, therefore mode dispersion is greatly reduced, more signal transmission bandwidth of up to 100m in 2.5Gbps in recent years, GIPOF has become the main direction of POF research.
Over six cable manufacturers even the rapid development of optical fiber technology, optical fiber in optical communication applications but there are many problems to be solved, such as dispersion and dispersion, dispersion and dispersion slope, small negative dispersion, polarization mode dispersion, nonlinearity, large core area of bending loss, comprehensive optimization of contradiction, the effective area and dispersion the slope and negative dispersion and loss, so we must continue to carry out technical innovation to solve the problem, believe that with the passage of time, will strive for further improvement of optical fiber technology.