Abstract: A low cost L-band EDF (erbium doped fiber) amplifier offering high safety for human beings. Signal light and forward pumping light enter from the front end of the EDF. Amplified signal light exits and backward pumping light enters from the rear end of the EDF. The signal light that exits the rear end of the EDF isoutput from an optical connector. The power of the output signal light is set to its normal value when an optical fiber is connected to the optical connector, but is reduced to a level safe for the human body when an optical fiber is not connected to the optical connector. When the output signal light power is reduced, the forward pumping light power is reduced to a prescribed value that is not zero, and the backward pumping light power is reduced to zero. Where the backward pumping light power is zero, the output signal light power depends solely on the forward pumping light power. Therefore, the output signal light power can be reduced to a safe level using a simple control circuit.

Abstract: A hybrid amplifier reduces the noise generated by the hybrid amplifier. The hybrid amplifier includes a rare-earth doped fiber amplifier such as an EDFA (erbium-doped fiber amp), a Raman amplifier, a controller and a memory device. Noise is reduced by determining a gain balance between the EDFA and Raman amp that minimizes the noise figure. The controller performs a method that generates a plurality of functions relating the hybrid amp noise figure and the Raman gain for a particular span loss. These functions are then utilized to determine the Raman gain portion of the gain balance that minimizes the noise figure. The remaining portion of the gain balance is made up by the EDFA. For a hybrid amplifier that will see only one span loss value, then only one such function needs to be generated. Furthermore, the memory device of the hybrid amplifier can be programmed to store an optimum control curve that minimizes the noise figure for one or a plurality of span losses.

Abstract: Novel optical amplifier designs are disclosed. The optical amplifier generally comprises an amplification section having an anti-reflection coating on a first end face and a reflector optically coupled to a second end face. The amplification section of the amplifier interacts with the input and reflected optical signals to produce an amplified optical signal. The amplification section may include rare earth doped glass amplifiers (e.g., erbium-doped amplifiers), rare earth doped waveguide amplifiers (e.g. erbium-doped waveguide amplifiers), polymer amplifiers or parametric amplifiers. The amplifier may include a waveguide structure proximate the amplification section to confine optical signals within the amplification section and/or guide signals into and out of the amplifier. The amplifier may be combined with optical components for coupling signals between optical fibers and the amplifier. The waveguide may have a modified “V” shape where the “V” with at two legs.