788 research outputs found
Tunable picosecond frequency-shifted feedback fiber laser at 1550 nm
No full textA novel frequency-shifted feedback (FSF) fiber laser cavity is proposed and experimentally verified. The laser generates stable mode-locked pulses of <2 ps, mainly limited due to chirp induced by the frequency-shifting element (i.e., the acoustooptic modulator) on the pulses. Fourier transform-limited subpicosecond pulses were obtained by compensating this excess chirp using a piece of single-mode fiber SMF-28 outside the laser cavity. The unique cavity design also allow us to tune the pulse wavelength throughout the Er-gain band and the ability of the laser to self-start gives us the opportunity to characterize transient behavior of mode-locked pulses in an FSF fiber laser cavity
250 GHz intensity modulation via Raman gain in the soliton regime
No full textWe have analysed the performance of all-optical intensity modulator operating in the soliton regime. We have shown that the effect of self-phase modulation limits the maximum speed of this nonlinear modulator to ~300GHz
All-fiber spatial mode selective filter for compensating mode dependent loss in MDM transmission systems
No full textWe 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
No full textWe 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
No full textStep-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
Cascaded nonlinearity: a simple technique to compensate Kerr effect in optical amplifiers
No full textWe have experimentally demonstrated a hybrid optical amplifier comprising a periodically poled LiNbO3 and an erbium-doped fibre amplifier. The use of cascaded nonlinearity inside nonlinear crystal made possible to construct a "nonlinearity-free" optical amplifier
All-fibre DFB laser WDM transmitters with integrated pump redundancy
No full textPump failure safe 8 and 16 channel WDM transmitter arrays based on all-fibre DFB lasers are demonstrated. Each WDM channel in the modules remain in operation despite the drop out of several pump diodes
All-fiber, ultra-wideband tunable laser at 2µm
No full textWe report a direct diode-pumped all-fiber tunable laser source at 2µm with a tuning range of more than 250nm. A 3dB power flatness of 200nm with a maximum output power of 30mW at 1930nm was achieved. The laser has a high optical signal-to-noise ratio (OSNR) of more than 40dB across the whole tuning range
Q-switched 980nm Yb-doped fiber laser
No full textA Q-switched 980nm cladding-pumped ytterbium-doped single-mode fiber laser reached 1.2µJ of energy and 100W of peak power in 20ns pulses and repetition rates of 0.65MHz at 0.25W of average output power
Optical amplifiers for SDM communication systems
No full textWe review recent progress on the implementation of multi-spatial channel optical amplifiers and associated passive components for SDM transmission systems.</p
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