All-fiber spatial mode selective filter for compensating mode dependent loss in MDM transmission systems

We propose and demonstrate a simple all-fiber spatial mode selective filter based on splicing a short segment of small-core SMF between two few-mode fibers. An 8dB MDL equalization range with less than 2dB IL is demonstrated for a 2-mode fiber device

16-µJ pulse energy, picosecond, narrow-linewidth master oscillator power amplifier using direct amplification

We present a gain-switched-diode-seeded 1034.5nm master oscillator power amplifier, employing direct amplification through standard commercial Yb3+-doped fibres to generate 15.6µJ-pulse-energy, 126kW-peak-power, picosecond pulses with 3dB spectral bandwidth of 0.87nm

Experimental demonstration of single-mode large mode area multi-trench fiber for UV-VIS light transmission

Step-index optical fibers are widely used waveguides for light transmission. However, non-linear effects are always a severe challenge for optical fibers with increasing power level. This challenge is more severe at shorter wavelengths, where core size has to be much smaller in order to maintain a single mode operation. For an example, for 0.005 core refractive index with respect to cladding, a 10µm core diameter can ensure single mode operation at 1550nm. On other hand, core diameter has to be ~4µm and ~2µm at lambda=632nm and 300nm respectively for single mode operation. At these shorter wavelengths, photonic crystal fiber (PCF) and hollow core photonic bandgap fiber (HC-PBGF) have been proposed to address non-linear effects by offering large core diameter and air-core respectively [1-2]. However, such fibers are relatively difficult to fabricate. Moreover, presence of air-holes causes considerable difficulties in cleaving and splicing.Recently, we proposed an all-solid fiber design known as multi-trench fiber (MTF) as shown in Fig. 1(a) [3]. In this paper, we demonstrated their mode area scaling capability for UV-VIS wavelengths. Numerical simulations show the potential of achieving an effective single mode for 10µm and 20µm core diameter MTF by ensuring high loss to the higher order modes (HOMs) at ~300nm and ~632nm respectively. Fig. 1(b) shows numerically computed bending loss of a 20µm core MTF with trench thickness (t)=1.34µm, refractive index difference between core and cladding (Delta.n)=0.005, and resonant ring thickness (d)=6µm at 632nm. It is important to note that MTF ensures similar level of loss (as shown in Fig. 1(b)) to the HOMs even in an unbent case thanks to the resonant coupling between modes of core and resonant ring, which ensures suitability for beam delivery applications. Fig. 1(c) shows the RIP and microscope image of a 20µm core MTF fabricated by MCVD process in conjunction with rod-in-tube technique. Fig. 1(d) shows the measured bending loss of fiber. The loss remains lower than 0.2dB/m and 0.5dB/m at ~30cm and ~15cm bend radius respectively at ~632nm. This loss can even be reduced down with further refinement in fabrication process. We investigated the output profile of a 2m long MTF using the experimental set-up shown in Fig. 1(e) with respect to the multi-mode input beam as shown in Fig. 1(g). Fig. 1(f) shows the output for different offset launching, while fiber is coiled at ~20cm bend radius. On the other hand, Fig. 1(h) shows the output at different coil radii for optimum launching. In this paper, for the first time, to the best of our knowledge, an effective-single-mode behaviour of an all-solid and cylindrical symmetrical fiber of a large core (~20µm) fiber at ~632nm has been demonstrated. All-solid design and cylindrical symmetry ensure suitability for mass-scale production and easy cleaving and splicing. Further, with these advantages, a large core (~10µm) MTF at ~300nm as confirmed by our simulations can also be achieved and details will be presented at conference

Effect of high and low cost brood feeds on gonado-somatic index and fecundity of freshwater prawn Macrobrachium rogenbergii de Man

Studies were conducted to observe the effects of different types of feeds on the gonado-somatic index (GSI) and fecundity of freshwater prawn Macrobrachium rogenbergii. Three different treatments (T1 T2 and T3) were designed with three types of feed as follows: (i) Saudi-Bangla Prawn feed 100% - T1 (ii) SaudiBangla prawn feed 50%+ local feed 50%- T2 and (iii) local feed 100%- T3. The results showed that the average value of gonado-somatic index (GSI) was 14.39, 14.35 and 14.36 and the average fecundity of M. rogenbergiiwas 99,741, 98,125 and 97,911 in T1 T2 and T3 respectively. No significant difference (p>00.5) was between gonado-somatic indices (GSI) and fecundities of M. rogenbergii among different feeding trails. The price of Saudi-Bangla prawn feed was very high (Tk. 23/kg) than the local feed (Tk. 14/kg). So, use of local feed was recommended for M. rogenbergii brood rearing

Recent progress in the development of few mode fiber amplifier

We review the performances of both core and cladding pumped few-mode erbium doped fiber amplifiers supporting 6 spatial modes (4 mode groups) which incidentally the highest mode count demonstrated to date

Fiber-laser-pumped, high-energy, mid-IR, picosecond optical parametric oscillator with a high-harmonic cavity

We demonstrate the generation of high-energy, mid-IR, picosecond pulses in a high-harmonic-cavity optical parametric oscillator (OPO) that has a relatively compact cavity with a length that is a small fraction of that required to match the pump repetition rate. The OPO, based on an MgO-doped periodically poled LiNbO3 crystal, is pumped by a fiber master-oscillator-power-amplifier system employing direct amplification and delivering 11µJ, 150ps pulses at 1035nm. For a 1.554-m long OPO cavity, resonating near-infrared signal pulses with a repetition rate that is the 193rd harmonic of the 1MHz pump are demonstrated. The mid-infrared idler output pulses, tunable from 2300nm to 3500nm, are generated at a 1 MHz repetition rate and have energies as high as 1.5µJ

Amplification of 12 OAM states in an air-core EDF

We propose the amplification of 12 OAM modes in an air-core EDF using either core- or cladding- pumping at 980nm. Differential modal gains of only 0.25dB among all the 12-modes are achieved over the C-band

Extreme short wavelength operation (1.65 - 1.7 µm) of silica-based thulium-doped fiber amplifier

We report the first demonstration of silica-based thulium-doped fiber amplifier (TDFA) working in the 1.65 - 1.7 µm waveband. Up to 29 dB small signal gain and noise figure as low as 6.5 dB are achieved

Inspection of defect-induced mode coupling in hollow-core photonic bandgap fibers using time-of-flight

We analyze defect-induced mode coupling in a hollow-core photonic bandgap fiber using time-of-flight, and show its utility in complementing optical time-domain reflectometry

Experimental characterization of a graded-index ring-core fiber supporting 7 LP mode groups

We design and characterize a graded-index-ring-core fiber supporting 7 LP modegroups (13 spatial modes) for mode multiplexed transmission with low MIMO processing complexity. Spatial and temporal modal properties are analyzed using an SLM-based mode multiplexer/demultiplexer