What Is EDFA & PDFA For CATV Headend System ? How EDFA PDFA Works ?

Earlier LCOs were getting feed from the MSO via Coaxial cables.Then LCOs implement the amplifiers to get the signal at longer distance.It was very complex system in cable tv distribution system.If you are using the coaxial cable then interference chances are high than the Optical Fiber Cable.

It was very expensive system.Because now a days we can purchase fiber more cheaper than the coaxial cable.A 4 core fiber is more cheaper than the good quality RG 6 coaxial fiber.Thus fiber optical solution is very cheaper than the coaxial solution.

Attenuation is very low in fiber.So there is no need to use amplifiers for short distances. OFC have low interference value approximate to zero.So OFC is more reliable than coaxial.

What Is PDFA

PDFA stands for Praseodymium Doped Amplifier. PDFA in cable tv industry have the wavelength of 1310 nm.It is very convenient to use.These transmitters are mounted at MSO to provide optical signal in whole city.Some LCOs also use these transmitter for to send their signal at long distance.To better understand the ordinary transmitter or PDFA we need understand power distribution system.

We are having here an example how optical power distribution system works,

As you can see above in the figure we have splitted +2 dBm optical power into two parts of -1 dBm by using 50:50 splitters. Then again this -1 dBm power have splitted into four points each one having -4 dBm power by using 50:50 splitters.

The power is getting down due to splitter losses.Thus as we can see above in the figure if we are receiving + 2dBm power then it gives four trunk points of -4 dBm.-4 dBm power can go approx 3 km.After 3 km lco needs to use NODE by giving this input of -4 dBm. Then lco gets RF output from NODE and he distribute signals in field.

Generally NODE have input power of 0 dBm but there are some FO NODES available in the market which can have low power of -4 dbm easily and can give RF output.

Thus as we discussed above there is limitation of power (-4 dBm ) and this limited power we can send at limited distance.This is -4 dBm power is very low for a operator.If LCO wants good quality of signal then he will install strong power NODE and that will accept power near about 0 dBm. As we have seen 0 dBm power is not available there so we need more power for better quality.

Thus we need to use EDFA.

What are splitters dividers combiners

What Is EDFA

EDFA stands for Erbium Doped Fiber Amplifier. EDFA works of 1550 nm wavelength. EDFA is upgraded version of PDFA. EDFA receive the optical input and give optical output while PDFA receive RF input and give optical output. EDFA receive 0 dBm optical input. There are many types of EDFA available which gives different optical output levels. EDFA is costly device rather than PDFA.

To better understand the EDFA we need to have an example,

As we can see above in the figure that MSO is giving 0 dBm as optical input to EDFA. Then EDFA is giving +18 dBm optical power as output.These splitters are 50:50.

Thus we are having four points as output of +12 dBm. So we giving 0 dBm and it is providing four trunk lines of +12 dBm which sufficient.

Instead of 4 points of output if we require 8 points at output then the power will be +9 dBm per point.

Note

You can not provide more than +13 dBm power to a fiber.

If you are planning to implement EDFA in your network then you should have 1550 nm fiber optic feed.

+17 dBm power can be send in fiber by SBS compensation.

EDFA needs more maintenance of fiber than PDFA.

This is all about EDFA And PDFA.

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