The main differences of single-mode fiber

These are the types of standards specified by ITU for optical fibers:

G. 651 is a multimode optical fiber.

G. 652 is a conventional single-mode fiber with a zero dispersion point at 1300nm, where the dispersion is the smallest; According to PMD, it is also divided into G There are four types: 652A, B, C, and D.

G. 653 is a dispersion shifted fiber (DSF) with 1550nm as the zero dispersion point. The principle is to shift the dispersion through waveguide dispersion, so that low loss and zero dispersion are at the same operating wavelength. However, zero dispersion is not conducive to multi-channel WDM transmission because when there are a large number of multiplexed channels and the channel spacing is small, a nonlinear optical effect called four wave mixing (FWM) will occur, which mixes two or three transmission wavelengths and generates new and harmful frequency components, leading to crosstalk between channels. If the dispersion of the fiber optic line is zero, the interference of FWM will be very severe; If there is trace dispersion, FWM interference will actually decrease. In response to this phenomenon, scientists have developed a new type of optical fiber, NZ-DSF.

G. 654 fiber is an ultra-low loss fiber mainly used in transoceanic optical cables. Its core is pure silica, while ordinary fiber cores need to be doped with germanium. The minimum loss is around 1550nm, only 0.185dB/km, but the dispersion is relatively large in this region, about 17-20 ps/[nm * km], and the dispersion is zero in the 1300nm wavelength region.

G. 655 fiber is a non-zero dispersion shifted fiber (NZ-DSF), divided into 655A, B, and C. Its main feature is that the dispersion at 1550nm is close to zero, but not zero. It is an improved dispersion shifted fiber used to suppress four wave mixing.

G. 656 fiber is a future oriented fiber, and the working wavelength of G656 has significantly increased, including the S, C, and L bands (1460 to 1625nm).

G. 657 fiber optic, the International Telecommunication Union ITU-T published the standard recommendation "Characteristics of single-mode fiber optic cables and optical cables insensitive to bending losses for access networks" in December 2006, namely the G.657 fiber optic standard. G. 657 optical fibers are divided into Class A and Class B optical fibers. According to the principle of minimum bendable radius, the bending levels are divided into three levels: 1, 2, and 3. Among them, 1 corresponds to a minimum bending radius of 10mm, 2 corresponds to a minimum bending radius of 7.5mm, and 3 corresponds to a minimum bending radius of 5mm. Combining these two principles, G.657 fibers are divided into four subcategories: G.657.A1, G.657.A2, G.657.B2, and G.657.B3.

difference

1. Single mode transmission has a long distance

2. Multi mode transmission has a large bandwidth

3. Single mode does not experience dispersion, reliable quality

4. Single mode typically uses lasers as light sources, which are expensive, while multimode typically uses inexpensive LEDs

5. Single mode prices are relatively high

6. Multimode is cheap, and short-range transmission can