Optical amplifier site with reduced noise and transmission system utilizing such

An optical amplifier site connected to a distributed Raman amplifier fiber, said optical amplifier site comprising:

• (i) a distributed Raman amplifier pump module, connected to said distributed Raman amplifier fiber, such that said Raman amplifier fiber and said pump module form a distributed Raman amplifier that provides a first signal gain level;
• (ii) an optical amplifier located downstream from said distributed Raman amplifier, said optical amplifier being indirectly coupled to said distributed Raman amplifier, said optical amplifier including a first amplification medium, providing a second signal gain level;
• (iii) at least one active optical signal loss element located between said distributed Raman amplifier and said optical amplifier, said at least one active optical signal loss element contributing to optical loss of said amplifier site and providing a first amount of optical signal loss, said first amount of optical signal loss being at least 0.5 dB;
• (iv) a second amplification medium located down stream from said first amplification medium;
• (v) at least another one active optical signal loss element providing a second amount of optical signal loss, said at least another one active optical signal loss element being located between said first amplification medium and said second amplification medium;
• and (vi) wherein said amplifier site has an improved Noise Figure NF when compared to an amplifier site without said at least one active optical signal loss element located between said distributed Raman amplifier and said optical amplifier, so that all optical signal loss elements are situated between said first amplification medium and said second amplification medium, such that said the active optical signal loss elements that are being located between said first amplification medium and said second amplification medium provide an amount of loss that equals to the sum of the first amount of optical signal loss and the second amount of optical signal loss.

A transmission system comprising:

• (i) a distributed Raman amplifier that provides a first signal gain level of more than 10 dB;
• (ii) a discrete optical amplifier located downstream from said distributed Raman amplifier, said discrete optical amplifier being indirectly coupled to said distributed Raman amplifier, said discrete optical amplifier including a first amplification medium, providing a second signal gain level;
• (iii) at least one active optical signal loss element located between said distributed Raman amplifier and said optical amplifier, said at least one loss element contributing to optical loss of said amplifier site and providing at least 0.5 dB loss;
• (iv) a second amplification medium located down stream from said first amplification medium;
• (v) at least another one active optical signal loss element, said at least another one optical signal loss element being located between said first amplification medium and said second amplification medium.