Optical amplifying unit and optical transmission system

Method for amplifying optical signals, comprising the steps of:

• feeding the optical signals to an active fiber having a core codoped throughout with Er and Yb;
• and
• optically pumping, during the step of feeding the optical signals, the active fiber,
• characterized in that said step of optically pumping includes feeding throughout the core of said active fiber a first pump radiation for exciting Er and a second pump radiation for exciting Yb.

Optical amplifying unit including:

• an input (101) for the input of optical signals,
• an output (102) for the output of said optical signals,
• an active fiber (103) having a core codoped throughout with Er and Yb, optically connected to said input and said output, for amplifying said optical signals,
• a first and a second pump source (104, 106) for generating a first and, respectively, a second pump radiation, and
• a first and a second optical coupler (105, 107) for optically coupling said first pump source (104) and, respectively, said second pump source (106) to said active fibre,
• characterized in that said first pump radiation includes an excitation wavelength for Er and said second pump radiation includes an excitation wavelength for Yb, and the first pump radiation and the second pump radiation are fed throughout the core to excite Er and Yb, respectively.

An optical transmission system comprising:

• an optical transmitting unit for transmitting optical signals,
• an optical receiving unit for receiving said optical signals,
• an optical fiber link optically coupling said transmitting unit to said receiving unit and for conveying said optical signals, and
• an optical amplifying unit coupled along said link, for amplifying said optical signals, said optical amplifying unit comprising:
• an input for the input of said optical signals,
• an output for the output of said optical signals,
• an active fiber having a core codoped throughout with Er and Yb, having a first end optically coupled to said input and a second end optically coupled to said output, for the amplification of said optical signals,
• a first and a second pump source for generating a first and, respectively, a second pump radiation, and
• a first and a second optical coupler for optically coupling said first pump source and, respectively, said second pump source to said active fiber,
• wherein said first pump radiation includes an excitation wavelength for Er, said second pump radiation includes an excitation wavelength for Yb, and the first pump radiation and the second pump radiation are fed throughout the core to excite Er and Yb, respectively.

An optical amplifying unit comprising:

• an input for the input of optical signals,
• an output for the output of said optical signals,
• an active fiber having a core codoped throughout with Er and Yb, optically connected to said input and said output, for amplifying said optical signals,
• a first and a second pump source for generating a first and, respectively, a second pump radiation, and
• a first and a second optical coupler for optically coupling said first pump source and, respectively, said second pump source to said active fiber.
• wherein said first pump radiation includes an excitation wavelength for Er, said second pump radiation includes an excitation wavelength for Yb, and the first pump radiation and the second pump radiation are fed throughout the core to excite Er and Yb, respectively.