Optical amplifier

[koll]

Hi which type of design will be better for the following op amp placement:

1) In line amplifier
2)post amplifier
3)preamplifier

[alistu]

Hi koll,

I have read since the optical gain in a Raman amplifier is distributed over a long span of optical fiber, the optical pump is used at the end of a length of fiber to provide optical gain that increases towards the end of the fiber. So a Raman amplifier can be combined with an EDFA booster (to act as an in-line amplifier) or inline amplifier to produce a more uniform power along the length of fiber. I have seen EDFA being used in all stages. Also, hybrid optical amplifiers are deigned and used.

Regards

[Alessandro Festa]

Hi Koll,

can you explain a little bit more your question? When you say “design”, are you referring to the design of the whole system or to the design of only the amplifier?

Regards,

Alessandro

[koll]

The whole system. Thank you.

[Alessandro Festa]

Hi Koll,

1) inline amplifiers are tipically used in repeated systems (for example 1000km of 10x100km spans), they usually are required to have good NF, output power and mid-stage access in case of dispersion compensatio.
2) not sure I understand what post-amplifiers are…maybe you mean boosters?
3) preamplifiers are the last ones before the receiver section. These amplifiers need to have very good noise figure, while output power is usually low because their output goes directly (through demux) to the receivers. As Alitsu mentions, you can also use hybrid EDFA/Raman for preamplification of the optical signal.

[koll]

Hi another question.

If I want to design a 8 DWDM channels(with demultiplexer) from A to B using a SMF.(separation of each channel is 100GHz) What kind of amplification method should I used? Also what kind of transmission band will be suitable?

PS: if you don’t mind can you illustrate with a diagram.

[Alessandro Festa]

Hi Koll,

the method depends on the SMF lenght reach you want. Hybrid Raman+EDFA allows the longest link, but adds more cost.
Regarding the transmission band, with only 8 channels it is best to choose the band between 1550-1560nm where EDFAs have lower noise figure and SMF loss is low.

[koll]

Hi can I just used EDFA amplifier? Will it be enough to design a 8 DWDM channel with channel speparation of 100 GHZ. Do you have a a diagram example to design such channel?

And how do you decide the transmission band?

Thank You.

[alistu]

Hi Koll,

Since EDFA has relatively low noise in optical amplifiers, it can be used as preampliifer. Also, it is widely being used in the line as you have probably seen in many occasions. In terms of bandwidth, Raman ampliifer has a more flat gain in a wider range of wavelength compared to EDFA.
Regards

[Alessandro Festa]

Hi Koll,

the need of amplifiers depend on the transmission distance and bitrate you want to achieve, which set the sensitivity at the receiver end.
Can you specify your requirements?

[Author]

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