Basically what the secondary coating line solve may be the traditional distance problem like any long distance telecommunication system say for example a trans-Atlantic link. As optical signals travel through the fiber, the signals become weaker in power. The farther you are going, the weaker the signal become until it might be too weak to become detected reliably.
Fiber optic communication systems solve this concern by using fiber amplifiers as you go along. A repeater or amplifier is inserted in to the system in a point the location where the signal is becoming weak, to boost the potency of the signal so it may be transmitted through another period of fiber cable. Many amplifiers or repeaters may be placed in sequence to maintain the signal strong along the whole fiber link.
Traditionally, electronic repeaters were utilised for optical signal amplification. A repeater is an opto-electro-opto device. It converts a weak optical signal into electronic signal, cleans up the electronic signal, and after that converts the electronic signal straight back to optical signal by using a lightwave transmitter. The lightwave transmitter emits much stronger power compared to incoming optical signal and thus amplifies it.
However, it is an inconvenient and expensive process and which is why this has been replaced from the new optical fiber amplifiers technology.
An optical fiber amplifier can be a purely optical device. It doesn’t convert the incoming optical signal to electronic signal whatsoever. Basically, it is possible to think of it a in-line laser. And Sheathing line can simultaneously amplify lots of optical channels since they usually do not convert each channel into electronic signals separately.
The atoms of erbium or praseodymium might be pumped by high power light (pump laser) into excited state. But are not stable inside the excited state. As soon as the optical signals that need to be amplified pass even though fiber, they stimulate the excited erbium atoms. The erbium atoms will jump through the high power level excited state into low power level stable state, and release their energy as emitted light photons concurrently. The emitted photons have the identical phase and wavelength because the input optical signal, thus amplify the optical signal.
It is a very convenient method of amplifier for the optical fiber communication system because it is an in-line amplifier, thus removes the requirement to perform optical-electrical and electrical-optical conversion process.
The pump laser wavelengths and the corresponding optical signal wavelengths are key parameters for operation of fiber amplifiers. These wavelengths depend upon the sort of 12dextpky element doped in the secondary coating line and on the composition from the glass inside the fiber.
Another necessary term in understanding fiber amplifiers is its “gain”. Gain measures the amplification per unit period of fiber. Gain depends on the materials and the operating conditions, and it varies with wavelength for all those materials.
For low input powers, the output power is proportional on the gains times the fiber length. Thus, P(output) = P(input) x Gain x Length
For high input powers, the gain saturation effect is needed. So increment of input power produces less output power, which essentially means the amplifier has run out of the energy it requires to generate more output.