Multichannel Fiber Laser Research Articles

Multichannel fiber laser acoustic emission sensor system for crack detection and location in accelerated fatigue testing of aluminum panels

Detection and location of the source of acoustic emission in a thin aluminum panel is demonstrated using a multichannel fiber laser sensor system. Acoustic emission generated by a crack in an aluminum panel used as a test coupon in an accelerated fatigue experiment is detected and the location of the crack identified. Acoustic emission is detected over a bandwidth of around 0.5 MHz from a serially multiplexed array of four laser sensors and compared with measurements taken from four piezo-electric sensors co-located with the fiber laser sensors. The location of the crack is determined by first estimating time difference of arrival of signals at each sensor using a novel algorithm based on the cumulative distribution transform method with hyperbolic positioning. The fiber laser sensor is shown to match the signal-to-noise ratio of the industry standard (Mistras S9225) piezo-electric acoustic emission sensor.

Multichannel fiber laser Doppler vibrometer studies of low momentum and hypervelocity impacts

A multichannel optical fiber laser Doppler vibrometer was demonstrated with the capability of making simultaneous non-contact measurements of impacts at 3 different locations. Two sets of measurements were performed, firstly using small ball bearings (1mm–5.5mm) falling under gravity and secondly using small projectiles (1mm) fired from an extremely high velocity light gas gun (LGG) with speeds in the range 1km/s–8km/s. Determination of impact damage is important for industries such as aerospace, military and rail, where the effect of an impact on the structure can result in a major structural damage. To our knowledge the research reported here demonstrates the first trials of a multichannel fiber laser Doppler vibrometer being used to detect hypervelocity impacts.

Experimental validation of FWM efficiency improvement in multichannel fiber laser by using DF-HNLF

We proposed and experimentally reported on an efficient multiwavelength generation with narrow wavelength spacing based on four-wave mixing. The employment of dispersion flattened high nonlinear fiber (DF-HNLF) and double-pass configuration enable an efficient multiwavelength generation with a 3dB bandwith of ~11nm and a wavelength spacing of 0.1nm. Comparisons were made by inserting a 500m long standard single mode fiber (SSMF), a 500m long conventional high nonlinear fiber (HNLF) and a 500m long DF-HNLF into the cavity, respectively, to analyse the role of nonlinearity and dispersion. Compared with HNLF, an improvement of almost 200% was made in 3dB uniformity of output spectrum in our DF-HNLF based multiwavelength system.

Frequency-comb-referenced multi-channel fiber laser for DWDM communication

We propose an all-fiber-based multi-channel optical scheme that enables simultaneous generation of multiple continuous-wave laser wavelengths with stabilization to the frequency comb of a femtosecond laser. The intention is to produce highly stable, accurate wavelength channels with immunity to environmental disturbance so as to enhance the transmission capacity of dense wavelength division multiplexing (DWDM) communications. Generated wavelengths lie over a wide spectral range of 5 THz about 1550 nm, each yielding a narrow linewidth of less than 24 kHz with an absolute position uncertainty of ~2.24 × 10¹² (10 s averaging) traceable directly to the atomic Rb clock.

Synchronous mode-locking in multichannel fiber laser systems

Based on the numerical experiment techniques, we report the synchronous pulse generation in multichannel fiber laser systems. The laser arrays under study are conformed by two up to seven nonlinearly coupled doped fibers, separately pumped. Due to the nonlinear interaction between evanescent waves of the active modulated radiation in one of the fibers and the radiation in all other ones, the system achieves the time synchronization – in all channels – of the pulse generation. The characterization of these systems as well as the effect of symmetry breaking on the pulse characteristics are carried out.