Components of FDDI

I. The component of FDDI

Figure 1

As you can see from Figure 1, the components that make up FDDI should have at least the following parts:

1, fiber optic cable.

2, FDDI adapter.

3, FDDI adapter and fiber-connected connectors.

However, in order to make the network have strong adaptability, and can be as backbone of FDDI and the Department of the lower speed

20MB/S Ethernet are connected and require a variety of interconnect devices. The components of this type have the following:

1, fddi-ethernet Network Bridge.

2, FDDI concentrator.

3, optical bypass device.

1. Fiber optic cable (interpretation of the first phase)

We know that the optical fiber can be divided into multimode fiber and single-mode fiber according to the propagation mode of light in the fiber. Single mode

Fiber has higher transmission rate and longer transmission distance than multimode fiber. The core diameter of Single-mode fiber is 8 to 10μm,

The cladding diameter is 125μm, the multimode light core diameter is 62.5μm, the cladding diameter is 125μm, and is usually written as

62.5/125μm. The cladding layer has different refractive index (R1), and its value is usually less than 1% of the fiber core. If the light

The angle of incidence less than the critical angle shoots into the core and cladding interface, and the light will be absorbed through the cladding into the coat.

The use of optical fiber as a transmission media must be equipped with photoelectric conversion equipment, namely, optical transmitter and optical receiver. The optical transmitter will

The encoded data to be sent is converted to a string of light signals to carry the data. FDDI Standard x3t9.5 stipulates that the optical transmitter uses

Optical diodes (LEDs) or laser diodes (LD). LED for multimode fiber, LD for single mode fiber. The receiver is usually

The optical detector is used to convert a foreign optical signal into an electric signal. An important property of the optical detector is the receiving sensitivity, which

Is the minimum power that the external light signal makes the receiver work must have. It should be noted that the receiver sensitivity is for a certain range

Wavelength of light.

The wavelength of light refers to the approximate wavelength of the light rays that are used to carry data on the optical fiber. The light emitting light at a certain set of wavelengths

Line. The Wavelength measurement unit is nm. In FDDI technology, the light emitted by the transmitter is about 1300nm in wavelength, as shown in Figure 2.

The optical power emitted by the optical transmitter is scattered in a certain range, and the central wavelength is the nominal light wavelength. As can be seen from fig. 2, the light dispersion

The range of the laser beam is narrower when the LD is used as the light source, while the LED is wider than the light source.

Figure 2

As the light travels along the optical fiber in the conductor, its strength decreases, which is attenuation. Fiber chain

The attenuation of the road is determined by the unit decay amount and the link length. The unit attenuation amount is the decay of the specified unit length, the unit

to DB. According to FDDI Standard, when the wavelength is 1300nm, the maximum attenuation of 1km is 1.5dB.

Another parameter for measuring fiber attenuation is the power budget, which has a power budget that is sensitive to the minimum transmit power and receiver

Degree decision. FDDI standard stipulates a power budget of 11dB.

It should be emphasized that the attenuation of optical power in addition to the loss of transmission along the optical fiber, light through the connector and the connector is the same

will also produce loss. The loss introduced at connectors and joints is called Power degradation (penalty). In each of the above

The total loss that can still maintain system work under the maximum loss quantity introduced by the link is called the link loss budget, it is the minimum transmitter work

Rate and receiver sensitivity minus any power deterioration.