Optical fiber transmission equipment transmission mode can be simply divided into: multimode optical fiber transmission equipment and single mode optical fiber transmission equipment.
1. Multimode optical fiber transmission equipment adopted by the device is the LED light, usually by the wavelength can be divided into two wavelength of 850 nm and 1300 nm, according to the output power can be divided into ordinary LED and improved leds - ELED. Multimode optical fiber used in the optical fiber transmission, which has two kinds of 62.5 mm and 50 mm.
In multimode optical fiber transmission decided to transmission distance are the main factors of the bandwidth of the fiber optic and LED the working wavelength, for example, if the working wavelength of 1300 nm LED and 50 micron fiber, its transmission bandwidth is 400 MHZ. Km, link attenuation of 0.7 dB/km, if the baseband transmission frequency is 150 MHZ, F to power for the fine - 18 dBm, receiving sensitivity for 25 dBm optical fiber transmission system, its biggest link loss is 7 dB, can be calculated:
ST connector loss:
2 db (two ST connector)
Optical loss allowance: 2
The theoretical transmission distance:
L = (7 dB - 2 dB - 2 dB) / 0.7 dB/km = 4.2 km
L as the transmission distance, and according to the bandwidth of the fiber:
L = B/F = 400 MHZ. Km / 150 MHZ = 2.6 km
Which is suitable for optical fiber bandwidth B, F baseband transmission frequency, then the actual transmission test, L on 2.6 km, therefore, decided to transmission distance are the main factors of the bandwidth of the multimode fiber.
2. The single-mode transmission equipment optical device is adopted by the LD, usually by the wavelength can be divided into two wavelength of 850 nm and 1300 nm, according to the output power can be divided into ordinary LD, high power LD, DFB LD (distributed feedback optical device). The optical fibers first used by single mode optical fiber transmission is the most common form of g. 652, the wire diameter for 9 microns.
1310 nm wavelength of light in g. 652 optical fiber transmission, to determine the transmission distance limit attenuation factor; Because under the 1310 nm wavelength, the material dispersion and the structure of optical fiber dispersion offset the total dispersion of 0, on the 1310 - nm wavelength optical signals with small amplitude can achieve broadband transmission.
1550 nm wavelength of light in g. 652 optical fiber transmission attenuation factor is very small, from a purely attenuation factor consideration, 1550 nm wavelength of light in the same light power transmission distance is greater than 1310 nm wavelength of the light transmission distance, but it's actually not the case, single-mode optical fiber bandwidth and the relationship between the dispersion coefficient D B is:
B = 132.5 / (DlxDxL) GHz
In which L is the length of the fiber, Dl as linewidth, for 1550 - nm wavelength of light, its dispersion factor such as table 3 to 20 ps/(nm) km), assuming that the spectral width is equal to 1 nm, transmission distance of L = 50 kilometers, there are:
B = 132.5 GHz = 132.5 MHz (DxL)
That is to say, to simulate waveform, using 1550 - nm wavelength of light, when the transmission distance of 50 km, transmission bandwidth is less than 132.5 MHz, if the baseband transmission frequency F 150 MHz, the transmission distance is less than 50 km, and actual applications, the linewidth of light source is often greater than 1 nm.
Can be seen from the type, the 1550 - nm wavelength of light in g. 652 optical fiber transmission to determine the transmission distance restricted mainly by dispersion factor.
1. Multimode optical fiber transmission equipment adopted by the device is the LED light, usually by the wavelength can be divided into two wavelength of 850 nm and 1300 nm, according to the output power can be divided into ordinary LED and improved leds - ELED. Multimode optical fiber used in the optical fiber transmission, which has two kinds of 62.5 mm and 50 mm.
In multimode optical fiber transmission decided to transmission distance are the main factors of the bandwidth of the fiber optic and LED the working wavelength, for example, if the working wavelength of 1300 nm LED and 50 micron fiber, its transmission bandwidth is 400 MHZ. Km, link attenuation of 0.7 dB/km, if the baseband transmission frequency is 150 MHZ, F to power for the fine - 18 dBm, receiving sensitivity for 25 dBm optical fiber transmission system, its biggest link loss is 7 dB, can be calculated:
ST connector loss:
2 db (two ST connector)
Optical loss allowance: 2
The theoretical transmission distance:
L = (7 dB - 2 dB - 2 dB) / 0.7 dB/km = 4.2 km
L as the transmission distance, and according to the bandwidth of the fiber:
L = B/F = 400 MHZ. Km / 150 MHZ = 2.6 km
Which is suitable for optical fiber bandwidth B, F baseband transmission frequency, then the actual transmission test, L on 2.6 km, therefore, decided to transmission distance are the main factors of the bandwidth of the multimode fiber.
2. The single-mode transmission equipment optical device is adopted by the LD, usually by the wavelength can be divided into two wavelength of 850 nm and 1300 nm, according to the output power can be divided into ordinary LD, high power LD, DFB LD (distributed feedback optical device). The optical fibers first used by single mode optical fiber transmission is the most common form of g. 652, the wire diameter for 9 microns.
1310 nm wavelength of light in g. 652 optical fiber transmission, to determine the transmission distance limit attenuation factor; Because under the 1310 nm wavelength, the material dispersion and the structure of optical fiber dispersion offset the total dispersion of 0, on the 1310 - nm wavelength optical signals with small amplitude can achieve broadband transmission.
1550 nm wavelength of light in g. 652 optical fiber transmission attenuation factor is very small, from a purely attenuation factor consideration, 1550 nm wavelength of light in the same light power transmission distance is greater than 1310 nm wavelength of the light transmission distance, but it's actually not the case, single-mode optical fiber bandwidth and the relationship between the dispersion coefficient D B is:
B = 132.5 / (DlxDxL) GHz
In which L is the length of the fiber, Dl as linewidth, for 1550 - nm wavelength of light, its dispersion factor such as table 3 to 20 ps/(nm) km), assuming that the spectral width is equal to 1 nm, transmission distance of L = 50 kilometers, there are:
B = 132.5 GHz = 132.5 MHz (DxL)
That is to say, to simulate waveform, using 1550 - nm wavelength of light, when the transmission distance of 50 km, transmission bandwidth is less than 132.5 MHz, if the baseband transmission frequency F 150 MHz, the transmission distance is less than 50 km, and actual applications, the linewidth of light source is often greater than 1 nm.
Can be seen from the type, the 1550 - nm wavelength of light in g. 652 optical fiber transmission to determine the transmission distance restricted mainly by dispersion factor.