kHz-order linewidth controllable 1550 nm single-frequency fiber laser for coherent optical communication

Abstract

A kHz-order linewidth controllable 1550 nm single-frequency fiber laser (SFFL) is demonstrated for the first time to our best knowledge. The control of the linewidth is realized by using a low-pass filtered white Gaussian noise (WGN) signal applied on a fiber stretcher in an optical feedback loop. Utilizing WGN signals with different signal amplitudes An and different cutoff frequencies fc, the linewidths are availably controlled in a wide range from 0.8 to 353 kHz. The obtained optical signal-to-noise ratio (OSNR) is more than 72.0 dB, and the relative intensity noise (RIN) at frequency greater than 40 MHz reaches -148.5 dB/Hz which approaches the shot noise limit (-152.9 dB/Hz). This kHz-order linewidth controllable SFFL is meaningful and valuable, for optimizing the receiver sensitivity and bit error rate (BER) performance of the coherent optical communication system based on high-order quadrature amplitude modulation (QAM).

Switchable single and dual-wavelength single longitudinal mode Pr:YLF laser at 607nm and 604nm

“…Solid state single longitudinal mode (SLM) laser with visible light band has broad development prospects in application elds such as high-resolution Raman spectroscopy, laser detection and Brillouin microscopy due to its characteristics of SLM output, narrow spectral line-width and long coherence length [1][2][3][4][5][6], and has become a relatively hot research direction in the world. At present, the visible SLM laser usually adopts nonlinear frequency transformation method to achieve the visible light band conversion.…”

Narrow-Linewidth Laser Linewidth Measurement Technology

“…Narrow-linewidth lasers with extremely low phase noise and a large coherence length have been widely used as a high-spectral-purity light source in gravitational wave detection [1,2], optical atomic clocks [3,4], lidar [5,6], high-speed coherent optical communication [7,8], and distributed optical fiber sensing [9,10]. The main reason for the linewidth generation is the phase fluctuation caused by spontaneous radiation [11] and the noise induced by mechanical and temperature factors [12,13].…”

Polarimetric parity-time symmetry in a photonic system

“…For a high-performance continuous-wave laser, singlemode operation is one of the fundamental requirements because it determines the coherence and power stability of the laser output 5,6,16 . For a long-cavity laser, for which it is preferable to have low phase noise, a narrow linewidth, and high optical power, single-mode lasing is challenging due to the small mode spacing 5,6,[16][17][18][19][20][21][22][23][24] . Since the gain spectrum of a gain medium in a laser cavity is usually several orders of magnitude broader than the mode spacing of the laser, the round-trip gain difference between adjacent modes is small, making it difficult to achieve single-mode oscillation by manipulating the lasing threshold 5,6 .…”

“…An optical filter can be incorporated into a laser cavity to reduce the number of modes above the threshold. If the optical filter has a sufficiently narrow passband, single-mode lasing can be achieved 23,24 . However, for a long-cavity laser such as a fiber laser with a cavity length on the order of tens of meters, a high-Q optical filter is needed, making the system costly and endowing it with poor stability 25,26 .…”