Self-Starting, Passively Modelocked Figure Eight Fiber Laser

A passively modelocked figure-eight fiber laser comprising

• a uni-directional fiber loop and a bi-directional fiber loop mirror coupled together by a 2×2 central coupler to create a figure-eight configuration,
• the uni-directional fiber loop comprising:
• a section of rare-earth doped fiber;
• a section of single mode fiber coupled to the section of rare-earth doped fiber to form a fiber loop;
• an input coupler disposed at an input termination of the section of rare-earth doped fiber for introducing a pump beam into the rare-earth doped fiber for amplifying an optical signal propagating therethrough;
• an output coupler disposed along the section of single mode fiber for out-coupling optical pulses created by the passively modelocked figure-eight fiber laser;
• and
• a bandpass filter disposed along the section of single mode fiber;
• the bi-directional fiber loop mirror comprising:
• a section of single mode fiber;
• and
• a section of Raman fiber coupled to the section of single mode fiber to form a loop mirror, the section of Raman fiber having a predetermined length L selected to impart a known dispersion value to the optical signal propagating therethrough;
• the 2×2 central coupler defined by a coupling ratio and configured to self-start into a passively modelocked low noise mode for generating optical pulses as an output, the figure-eight fiber laser further configured to self-start in a low noise mode by controlling one or more operating parameters selected from the group consisting of:
• the coupling ratio of the 2×2 central coupler, the coupling ratio of the output coupler, an accumulated, group velocity dispersion (GVD) of the figure-eight fiber laser based upon the accumulated dispersion associated with the sections of single mode fiber and the Raman fiber, and characteristics of the bandpass filter.