Wide band erbium-doped fiber amplifier (EDFA)

A wide band optical amplifier, comprising:

• a first erbium-doped fiber amplifier stage (S1) having an input and an output;
• a first pump light source coupled to the input of said first S1 for introducing a pump light;
• a second erbium-doped fiber amplifier stage (S2) having an input and an output;
• a second pump light source coupled to the input of said S2 for introducing a pump light;
• a split section disposed between said first S1 and said second S2 wherein an amplified signal light that enters said split section is split into a plurality of sub-band signals;
• a reflector for reflecting the amplified output signal from said S2 in a reverse traveling direction back into said second S2 and said first S1;
• a combiner for combining said reversely reflected amplified output signals and one of said sub-band signals output from said split section into an output signal;
• and,
• a circulator for forwardly passing input optical signals and for redirecting said reversely reflected amplified output signals to the input of said combiner.

A method of amplifying optical signals having two or more optical bands, the method comprising the steps of:

• (a) passing input optical signals through a first amplifier stage (S1);
• (b) splitting said amplified input signals into a C-band and L-band signals;
• (c) further amplifying said L-band signal in a second amplifier stage (S2);
• (d) redirecting said amplified L-band again back into said second S2 and said first S1 in a reverse direction;
• (e) amplifying said redirected L-band in said second S2 and said first S1;
• and,
• (f) recombining said redirected L-band and said splitted C-band to produce an output signal.