Single mode cable and Multimode cable

Single mode cable and multimode cable

Transmission of single-mode fiber optic cable

What single-mode fiber optic cables actually use for transmission is an intermediate fiber core, called an optical fiber. That is, single-mode optical cable is composed of optical fiber + outer sheath + intermediate medium. In fiber optic communications, a single-mode fiber (SMF) is an optical fiber that directly transmits optical signals in the transverse mode. Single-mode fiber operates at a data rate of 100M/s or 1 G/s, and the transmission distance can reach at least 5 kilometers.

Single-mode fiber: The central glass core is very thin (the core diameter is generally 9 or 10 μm), and only one mode of fiber can be transmitted. Therefore, its intermodal dispersion is very small, which is suitable for long-distance communication, but there are also material dispersion and waveguide dispersion, so the single-mode fiber has higher requirements on the spectral width and stability of the light source, that is, the spectral width should be narrow and stable.

Transmission of multimode fiber optic cables

Multimode fiber optic cables are mainly used for short distance fiber optic communications, such as in buildings or campuses. The typical transmission speed is 100M/s, the transmission distance can reach 2km, 1 G/s can reach 1000m, and 10 G/s can reach 550m. There are two types of indices of refraction: graded index and step index.

Multimode fiber: Fiber that transmits multiple modes at a given operating wavelength.

According to the distribution of its refractive index, it is divided into abrupt type and graded type. Since there are hundreds of modes transmitted in multimode fiber, the propagation constants and group rates of each mode are different, which makes the bandwidth of the fiber narrow, the dispersion large, and the loss also large. It is only suitable for short-to-medium distance and small-capacity optical fiber communication systems .

What is the difference between single-mode fiber optic cable and multi-mode fiber optic cable?

Model: GYFTY, GYFTZY are generally multi-mode; GYXTW, GYTS are generally single-mode.

Color: Indoor multi-mode optical cable is orange, indoor single-mode optical cable is yellow.

Identification: MM is multi-mode, SM is single-mode.

Transmission mode: Distinguish according to the transmission mode of light in the fiber.

Multimode Fiber Concept

Multimode fiber is a fiber that transmits multiple modes at a given working wavelength. When the geometric size of the fiber is much larger than the wavelength of the light wave, there will be dozens or even hundreds of propagation modes in the fiber. Different propagation modes have different propagation velocities and phases, resulting in time delay and widening of optical pulses after long-distance transmission. Therefore, the bandwidth of multimode fiber will be narrowed and its transmission capacity will be reduced, so multimode fiber is only suitable for optical fiber communication with small capacity.

Single Mode Fiber Concept

Generally, when v is less than 2.405, only one wave peak passes through the fiber, so it is called a single-mode fiber. Its core is very thin, about 8-10 microns, and the modal dispersion is very small. The main factor affecting the bandwidth of optical fiber transmission is various dispersion. The dispersion of single-mode fiber is small, so it can transmit light over a long distance with a wide frequency band, so single-mode fiber is especially suitable for large-capacity optical fiber communication.

Difference Between Multimode Fiber and Single Mode Fiber

1. Appearance color

The most obvious difference between single-mode fiber and multi-mode fiber is the color of the outer sheath. The single-mode fiber patch cord OS2 is yellow, while the multi-mode fiber OM1 and OM2 are orange outer sheath, OM3 is lake blue outer sheath, and OM4 is the outer sheath. Purple.

2. Fiber diameter

The core diameter of multimode fiber is generally 50µm (OM1) or 62.5µm (OM2, OM3, OM4), and the core diameter of single mode fiber is 9µm (OS2).

3. Light source

The light source of single-mode fiber transmission is laser, and the light source of multi-mode fiber transmission is LED.

4. Bandwidth

Multi-mode fiber narrows the bandwidth due to modal dispersion, while single-mode fiber allows only one mode to propagate in the fiber, and the rest of the high-order modes are all cut off, avoiding the problem of modal dispersion, so single-mode fiber has a very wide bandwidth. .

5. Price

The price of multi-mode fiber is cheaper than that of single-mode fiber. Because multi-mode fiber is suitable for short-distance transmission and relatively low cost, it is widely used in data centers, while single-mode fiber is suitable for long-distance transmission, so it is mainly used in backbone networks. and metropolitan area network.

6. Transmission distance

The transmission distance of multimode fiber is within 2KM, while the transmission distance of single mode fiber can reach hundreds of kilometers.

7. Application scenarios

Single-mode optical fibers are mainly used in metropolitan area networks, backbone networks, and PON scenarios, while multi-mode optical fibers are mainly used in scenarios such as enterprises and data centers.

In general, single-mode optical modules need to be used with single-mode fiber jumpers, and multi-mode optical modules need to be used with multi-mode fiber jumpers. In addition, indoor and short-distance applications are dominated by multi-mode fibers, and outdoor and long-distance applications are dominated by single-mode fibers