What Is Singlemode and Multimode Optical Fiber?

Light is an electromagnetic wave (visible light frequencies in the order of 10 ^ 14), singlemode fiber and multi-mode fiber optics are needed to explain fluctuations. The basic formula is the electromagnetic theory of Maxwell's equations, the boundary conditions of Fiber Optic Cables (size, refractive index, wavelength and other parameters) into Maxwell's equations.



The solution obtained contains numerous real and imaginary part, representing the spatial distribution of the electromagnetic field and the transmission, each solution can be called a mode, the real part can be interpreted as conductive portion for satisfied the total reflection conditions, it can be called the conduction mode. the imaginary part is rapid loss in the transmission swap, known as radiation modes. The solution with the fiber size, fiber core and cladding refractive index, the wavelength dependence of the incident light. When the fiber core size decreases, the mold can be found rapidly reduced conduction, in particular core size and wavelength may be compared, the conductivity is reduced to the mode field distribution is also a space appears discontinuous, showing the geometrical optics can not be explained. "quantum properties. "When reducing the fiber core size to a certain number, the only one possible conduction mode, this time, the optical fiber for this incident became a single-mode fiber.


 
Single Mode Fiber Patch Cable is relative, when the wavelength of the incident light is reduced, there will be a new conduction mode, this is relatively light, Fiber has become multimode fiber. So there is a cutoff wavelength of a single-mode fiber that is higher than this wavelength, which is the single-mode fiber. G 652 common singlemode fiber cutoff wavelength less than 1260nm.

Multimode Fiber Optic Cable can be understood as approximately the incident light along many different paths in the optical fiber transmission angles. Clearly different from the other end along the length of the different paths, because the length of the transmission time difference generated by different known mode dispersion (i.e. different paths in different modes).

Single mode optical fiber can transmit along a path (ie, only one mode), there is no mode dispersion. But with different refractive indices in different wavelengths of light in the same material, resulting in different transmission rate, so if the same beam of light contains different frequencies, the other end to the optical fiber transmission time is different, this causes the transmission time difference is called Single-mode dispersion or material dispersion or wavelength dispersive. Not the kind of light source is entirely monochromatic, the wavelength dispersion is widespread. We usually use several sources of communication, the wavelength dispersion smaller than the mode dispersion.

Common single-mode fiber (G 652) is about 8-10um core diameter, the related proudcts from Fiberstore, it's Duplex 9/125 sc to sc fiber patch cord. The picture is follow:

 

Sc to Sc Fiber Patch Cord is for high bandwidth and transmission rates over longer distances. This SC fiber patch cable is specifically designed for gigabit ethernet applications. The patented injection molding process provides each connection greater durability in resisting pulls, strains and impacts from cabling installs. Common multimode fiber core diameter, there are two types, 50um and 62.5um. The related products from Fiberstore, it's Duplex OM1 Multimode 62.5/125 Lc-Sc Fiber Patch Cable. The picture is follow:


Article Source From:http://www.cables-solutions.com

The Development and Benefits of Multi core Singlemode Fiber

1.

The development of multi core single mode fiber A typical optical fiber is single mode fiber structure, the outer cladding / inner cladding surrounding the core constitutes a waveguide. A common multi-core optical fiber includes a number of cores ,and each core have their own single-mode optical fiber inner cladding .Thus, each core is an fiber optic of the waveguide , i.e.,one singlemode fiber optic cable's function is be equal to a plurality of single core fiber . The obvious advantage of this fiber is low cost, low production costs of about 50% compared with ordinary fiber. In addition, Fiber optic cables can increase integration density , but also can reduce construction costs. Back in the late 1970s , foreigner proposed the idea which use multi-core optical fiber manufacturing high density fiber.However , because of the imperfect manufacturing technology , fiber affected by the residual stress , low mechanical strength , poor reliability, has not developed into practical and commercialization .Into the 1990s , fiber optic communication in the FTTH ( fiber to the home ) development has encountered higher cost of obstacles, and the intense competition in the copper.To overcome this obstacle , we must significantly reduce the cost of fiber optic cable manufacturing , and requires the development of high-density large armored fiber optic cable, in order to facilitate the laying of fiber optic cable and reducing installation costs . Thus, in 1994 , France Telecom proposed a new concept of multi core single mode and design a 4 core single mode fiber. In July 1994 made more than 100 kilometers Single Mode Fiber Cable, and use different core and structures fiber optic cables and non-fiber ribbon cable into the cable experiment. Compared with the common Single Mode Fiber, the cable density increase many times . Initially confirmed that the proposed multi core single mode fiber can reduce manufacturing costs while addressing the fiber optic cable and the development of high- density optical fiber optic cable. Since then, France Telecom and Alcatel have carried out a 4 core single mode optical fiber research and development , studyed from optical design, preform manufacture , drawing techniques , optical properties, a 4-pin cable, and mechanical connections from each a core of separation and termination of ordinary single-mode fiber and other aspects of a comprehensive. Currently, the cost per meter per core for $ 0.03 , while the cost per meter of ordinary single-mode fiber is $ 0.055. We can say that multi-core single-mode fiber forward practical development. This article focuses on the structure of multi-core single-mode optical fiber design, manufacturing processes and fiber properties, but also a brief introduction to the new fiber optic FTTH applications in the technical and economic advantages.

2.

Design of multi core singlemode fiber To meet the needs of FTTH systems. The design of multi-core fiber should meet the following key requirements: 1.31 um and 1.55um wavelength dual-window work; Crosstalk between each core is greater than -35 dB: precise geometry; Easy identification of each core and ordinary Single mode Fiber Optic Cable. Further, since the optical fiber length shorter in FTTH network (≤ l0 km), so the requirements for dispersion and attenuation of the fiber is relatively relaxed, there are strict requirements on bending and microbending losses. Each of the core are respectively located on the vertices of a square, the center of the square is the central axis of the multi core singlemode fiber. Each core is a single-mode optical fiber waveguides, cutoff wavelength 1.3 um.In order to reduce the bending loss and crosstalk, reinforce fiber molded capacity constraints, therefore compared with the conventional G652 optical fiber, the refractive index difference has increased. 3 core is a simple step structure, a refractive index difference 0.0062; another annular core refractive index profile, the refractive index difference 0.0l, this core is provided in order to facilitate identification of each of the cores.

The main advantage of multi-core Single Mode Fiber Cable

1. Attenuation coefficient By the testing and research of nearly 200km long fiber , the attenuation coefficient of the multi core singlemode optical fiber reached levels close to the corresponding single core fiber.

2. Bending and micro-bending loss characteristics Bending and microbending loss characteristics of the multi-core single-mode fiber optic is good, negligible additional loss introduced. This is due to the higher refractive index and limit the ability of a strong mold. Multi core single mode fiber optic in the l310nm and 1550nm wavelength mode field diameter was 8.4 ± 0.21un and 9.75 ± 0.25um, slightly smaller than the ordinary single mode optical fiber.

3. Crosstalk characteristics To 30 g of tension around 15 cm in diameter optical fiber on ferrule l0 km optical fiber with characteristic measurement, crosstalk between each core at l 310 nm wavelength, less than-70dB; at 1 550 nm wavelength, less than a 50 dB, are excellent -35 dB in the required index. Even slim to the 30 km, between 0-30g tension variations, changes, crosstalk is also only a few dB.

4. Mechanical strength Wth 10m length test, the average intensity of 70N. The conventional 125um fiber diameter of 60 N, it is because a large cross-sectional area of multi-core single-mode fiber. Fracture stress 4.6 GPa, 94% for the conventional 125 um diameter fiber.