Microwave

Harmonic

Quantum mechanics

Mode-locking

Frequency comb

Materials science

Dual loop

Telecommunications

Computer science

Acoustics

Picosecond

Phase noise

Injection locking

Laser

Physics

Multiplexing

Mathematics

Optics

Loop (graph theory)

Combinatorics

Fiber laser

Optoelectronics

Ultrashort pulse

Optics Letters

The active mode-locking (AML) technique has been widely used in erbium-doped fiber lasers to generate picosecond pulse trains. Here we propose a novel active mode-locking dual-loop optoelectronic oscillator (AML-DL-OEO), which can generate microwave frequency comb (MFC) signals with adjustable comb spacings. Based on this scheme, the order of harmonic mode-locking is dramatically decreased for a certain AML driving frequency compared with a single-loop AML-OEO. Thus, the supermode noise caused by harmonic mode-locking can be efficiently suppressed. In addition, the sidemodes are well suppressed by the dual-loop architecture. An experiment is performed. MFC signals with different comb spacings are generated under fundamental or harmonic mode-locking states. AML-DL-OEO systems with different length differences between two loops are implemented to evaluate supermode noise suppression capability. The performance of the generated MFC signals is recorded and analyzed.

Supermode noise suppression with polarization-multiplexed dual-loop for active mode-locking optoelectronic oscillator