Flat and compact switchable dual wavelength output at 1060 nm from ytterbium doped fiber laser with an AWG as a wavelength selector

A dual-wavelength ytterbium doped fiber laser with a narrowest spacing of 0.53 nm and widest spacing of 12.2 nm at 1064 nm is presented in this paper. An arrayed waveguide grating (AWG) together with an optical channel selector (OCS) have also been incorporated in the proposed setup that works as a switchable mechanism giving 23 different wavelength tunings. Producing an average output power of ?8 dB m and side mode suppression ratio (SMSR) of 59.65 dB, this dual-wavelength fiber laser is quite stable with an output power variance as low as 0.47 dB giving it an advantage due to its switching ability and stable dual-wavelength output powers.     

Tunable dual-wavelength fiber laser based on an opto-VLSI processor and four-wave mixing in a photonic crystal fiber

A stable wavelength and wavelength spacing tunable dual-wavelength fiber laser based on an Opto-very-large-scale-integration (Opto-VLSI) processor and four-wave mixing (FWM) in a high-nonlinear photonic crystal fiber is experimentally demonstrated. The results show that the line width of the tunable dual-wavelength fiber laser is 0.02 nm, and the wavelength spacing can be tuned from 0.8 nm to 4 nm with a 0.15 nm step. Under the influence of the FWM, the uniformity is below 0.6 dB and the measured side mode suppression ratio (SMSR) is above 45 dB.     

Tunable dual-wavelength erbium-doped fiber ring laser covering both C-band and L-band for high-speed communications

A simple, continuously tunable dual-wavelength erbium-doped fiber ring laser (TDEDFL) structure for applications in high-speed communication systems is proposed and experimentally demonstrated. The dual-wavelength tuning range is 58 nm covering both the C-band and L-band from 1547 to 1605 nm. We can not only obtain a 45% improvement over previously reported tuning ranges, but also tune the wavelength of each lasing output independently. The power equalization of the dual-wavelength outputs is less than 1.5 dB. We obtain extremely stable power variation and wavelength fluctuation at room temperature. Using this fiber laser, a 10-Gb/s data transmission over a 25-km single-mode fiber (SMF) can be made available with a power penalty of 0.5 dB is demonstrated with this laser.     

Synchronous tunable wavelength spacing dual-wavelength SOA fiber ring laser using Fiber Bragg grating pair in a hybrid tuning package

A Dual-Wavelength Semiconductor Optical Amplifier (DW-SOA) based fiber ring laser with synchronous wavelength tunability is proposed and experimentally demonstrated. The SOA gain medium strongly suppresses mode competition, thus allowing stable dual-wavelength laser oscillation. The wavelength spacing of the two lasers can be tuned synchronously using a modified hybrid-tuning package incorporating a pair of Fiber Bragg Gratings (FBGs). The DW-SOA demonstrates a laser output with a wavelength spacing of between 0.10 and 8.30 nm (wavelength shift inequality of 0.08 to 0.75 nm). The relationship between the applied strain and wavelength shift of the two tuning modes is also analyzed.     

Dual-wavelength S-band erbium-doped fiber double-ring laser

We propose and demonstrate an S-band CW dual-wavelength erbium-doped fiber (EDF) dual-ring laser using a compound-ring filter (CRF) with various coupling losses inside the gain cavity. Employing a ring filter combined within the cavity, the fiber laser can lase a dual wavelength without any filter inside the ring loop. The dual-wavelength output exhibits a good performance having optical side-mode suppression ratios (SMSRs) of 31.6 and 31.8 dB and output powers of ?9.6 and ?9.3 dBm at 1505.58 and 1506.43 nm, respectively, when the coupling loss is 30% inside the cavity. In addition, the output stabilities of the dual-wavelength laser have also been analyzed.     

Experimental study on tandem pumped fiber amplifier

We present the experimental results of a 1083 nm fiber amplifier tandem pumped by 1030 nm fiber laser. The output characteristics of the tandem pumped amplifier with cladding-pump and core-pump schemes are both investigated. The 1083 nm signal laser has not been efficiently amplified when cladding-pumped by 1030 nm laser for the weak absorption of the gain fiber. The core-pump scheme works well with the amplifier. The output properties with different gain fiber length are experimentally investigated. The maximum output power is 2.4 W with power conversion efficiency of 60%.     

Widely tunable compact erbium-doped fiber ring laser for fiber-optic sensing applications

A compact erbium-doped ring-shaped fiber laser suitable for fiber-optic sensing applications has been developed. The fiber laser utilized a tunable fiber Fabry–Perot filter as the tuning element and had a moderate milli-Watt level power output over almost the whole tuning range from 1530 to 1595 nm with a power fluctuation of 0.15 dB. High repetition rate scanning of laser operation over the whole tuning range was achieved at rates of up to 200 Hz. Moreover, the performance of the ring-shaped fiber laser configured with a high-concentration erbium-doped fiber was investigated for its larger wavelength tunability of over 100 nm. Output power characteristics of this ring-shaped fiber laser were also investigated when it worked in a scanning mode. A distorted power wavelength dependence, as well as some pulsing phenomenon were observed in scanning mode.     

Tunable microwave photonic notch filter using a dual-wavelength fiber laser with phase modulation

A novel tunable microwave photonic notch filter using a phase-modulated dual-wavelength fiber laser is presented. A stable dual-wavelength erbium-doped fiber laser with a linear cavity is formed by a polarization-maintaining uniform fiber Bragg grating (PM-FBG) and a polarization maintaining linearly chirped fiber Bragg grating (PM-LCFBG), both of which were fabricated on a high-birefringence (Hi-Bi) fiber. It is found that a stable room-temperature dual-wavelength operation can be achieved due to the presence of two reflection peaks arising from the orthogonal states of polarization (SOP) of the PM-FBG. Experimental results show stable dual-wavelength lasing operation with a wavelength separation of ∼0.36 nm and a large optical signal-to-noise ratio (OSNR) of over 40 dB under room temperature. The dual-wavelength fiber laser is combined with a phase modulator and a segment of single-mode fiber (SMF) as a dispersive device to form a tunable microwave photonic notch filter. By stretching the PM-FBG to tune the wavelength separation of the dual-wavelength fiber laser, a tunable microwave photonic notch filter with various free spectral ranges (FSRs) and a rejection ratio greater than 35 dB was developed.     

Tunable dual-wavelength fiber laser based on a polarization-maintaining fiber Bragg grating and a Hi-Bi fiber optical loop mirror

We demonstrate experimentally the operation of a linear cavity dual-wavelength fiber laser using a polarization maintaining fiber Bragg grating (PM-FBG) as an end mirror that defines two closely spaced laser emission lines. The PM-FBG is also used to tune the laser wavelengths. The total tuning range is ∼8 nm. The laser operates in a stable dual-wavelength mode for an appropriate adjustment of the cavity losses for the generated wavelengths. The high birefringence (Hi-Bi) fiber optical loop mirror (FOLM) is used as a tunable spectral filter to adjust the losses. The FOLM adjustment was performed by the temperature control of the Hi-Bi fiber.     

Ultra-broad and flat supercontinuum generation in short photonic crystal fiber combined with conventional fibers

In order to gain ultra-broad and flat super-continuum (SC) spectrum, we propose and demonstrate a new scheme. By coupling a train of short pulses with 100 fs width and 16.2 mW average power generated by a mode-locked laser into the scheme – short photonic crystal fiber (PCF) combined with conventional fibers. The SC spectrum has 491 nm bandwidth at −15 dBm below the spectral peak with ±0.5 dBm uniformity 100 nm in only 0.45 m PCF. The spectral bandwidth generated in the scheme increases 292 nm than spectrum generated in the two conventional fibers, and increases 152 nm than spectrum generated in the three convention fibers.     

A linearly-polarized tunable Yb-doped fiber laser using a polarization dependent fiber loop mirror

A Ytterbium-doped linearly-polarized fiber laser is constructed with a polarization maintaining fiber Sagnac loop mirror. The fiber loop mirror made of polarization maintaining fiber coupler has a polarization dependent reflectivity, which provides the necessary polarization discrimination between the slow and fast axes. With a fiber Bragg grating written in normal polarization maintaining fiber as an output coupler, laser output of up to 5.6 W at 1070 nm is generated with a polarization extinction ratio of > 20 dB and an overall efficiency of 55%. The broadband polarization dependent reflection of the fiber loop mirror offers advantages of easy spectral tuning and simple linearly-polarized laser generation.     

A 980 nm Yb-doped single-mode fiber laser pumped by a 946 nm Q-switched Nd:YAG laser

We demonstrate a 980 nm single-mode Yb-doped fiber laser with a 946 nm Q-switched Nd:YAG laser used as the pump source. The experimental arrangement exploited a 36.5 cm length of fiber and used the output from both ends of the cavity, providing a total average output power of 100 mW with a slope efficiency of 38%. In order to increase the coupling efficiency and the practicability of the fiber laser, another experimental setup with single ended output was studied, producing an average output power of 80 mW from a fiber length of 23.5 cm. The pulse duration is 10 ns at a repetition frequency of 16 kHz. The linewidth of the laser is 4 nm, ranging from 977 to 981 nm.     

Wide-band fanned-out supercontinuum source covering O-, E-, S-, C-, L- and U-bands

A wide-band supercontinuum source generated by mode-locked pulses injected into a Highly Non-Linear Fiber (HNLF) is proposed and demonstrated. A 49 cm long Bismuth–Erbium Doped Fiber (Bi–EDF) pumped by two 1480 nm laser diodes acts as the active gain medium for a ring fiber laser, from which mode-locked pulses are obtained using the Non-Polarization Rotation (NPR) technique. The mode-locked pulses are then injected into a 100 m long HLNF with a dispersion of 0.15 ps/nm km at 1550 nm to generate a supercontinuum spectrum spanning from 1340 nm to more than 1680 nm with a pulse width of 0.08 ps and an average power of ?17 dBm. The supercontinuum spectrum is sliced using a 24 channel Arrayed Waveguide Grating (AWG) with a channel spacing of 100 GHz to obtain a fanned-out laser output covering the O-, E-, S-, C-, L- and U-bands. The lasing wavelengths obtained have an average pulse width of 9 ps with only minor fluctuations and a mode-locked repetition rate of 40 MHz, and is sufficiently stable to be used in a variety of sensing and communication applications, most notably as cost-effective sources for Fiber-to-the-Home (FTTH) networks.     

Multi-wavelength bismuth-based erbium-doped fiber laser based on four-wave mixing effect in photonic crystal fiber

A stable multi-wavelength erbium-doped fiber laser based on four-wave mixing (FWM) in a photonic crystal fiber (PCF) is demonstrated in this paper. The phase matching condition for four-wave mixing in the photonic crystal fiber has been enhanced using a seed signal and a polarisation controller to control the states of polarisation in the ring laser cavity. At a maximum pump power of 1480 nm, 5 lines are observed with nearly 2.15 nm spacing between the lines, and with a signal to noise ratio of more than 20 dB. The number of channels and wavelength spacing can be controlled by varying the output coupler ratio.     

Supercontinuum generation using a passive mode-locked stretched-pulse bismuth-based erbium-doped fiber laser

A Supercontinuum (SC) generation in photonic crystal fiber (PCF) is demonstrated using an amplified picosecond stretched-pulses from a passive mode-locked Bismuth-based Erbium-doped fiber laser (Bi-EDFL). The Bi-EDFL employs of a piece of a highly nonlinear 49 cm long Bismuth-based Erbium-doped fiber (Bi-EDF), an optical isolator and a polarization controller in a cavity to generate a mode-locked stretched-pulse via a nonlinear polarization rotation technique. It operates at 1560 nm with a repetition rate of 42 MHz and a pulse width of 131 fs. The SC lights, which extends from 1250 nm to 1910 nm as well as in the visible green wavelength region are obtained with a 100 m long PCF and the amplified pump power of 30 dBm.     

All fiber passively mode locked zirconium-based erbium-doped fiber laser

All passively mode locked erbium-doped fiber laser with a zirconium host is demonstrated. The fiber laser utilizes the Non-Linear Polarization Rotation (NPR) technique with an inexpensive fiber-based Polarization Beam Splitter (PBS) as the mode-locking element. A 2 m crystalline Zirconia–Yttria–Alumino-silicate fiber doped with erbium ions (Zr–Y–Al-EDF) acts as the gain medium and generates an Amplified Spontaneous Emission (ASE) spectrum from 1500 nm to 1650 nm. The generated mode-locked pulses have a spectrum ranging from 1548 nm to more than 1605 nm, as well as a 3-dB bandwidth of 12 nm. The mode-locked pulse train has an average output power level of 17 mW with a calculated peak power of 1.24 kW and energy per pulse of approximately 730 pJ. The spectrum also exhibits a Signal-to-Noise Ratio (SNR) of 50 dB as well as a repetition rate of 23.2 MHz. The system is very stable and shows little power fluctuation, in addition to being repeatable.     

Dual-stage L-band erbium-doped fiber amplifier with distributed pumping from single pump laser

A dual-stage L-band erbium-doped fiber amplifier with a flat gain bandwidth over 36 nm is demonstrated using pump distribution technique. The pump power was distributed to two stages depending on the splitting ratio and the length of erbium-doped fiber that was used for this configuration. Both parameters are the key components for achieving a substantially flat gain response throughout the L-band region ranging from 1570 nm to 1605 nm. Although the input signal power was varied from ? 30 dBm to 0 dBm, gain of 17 dB with slight variations of less than 1.5 dB and a noise figure of less than 6.7 dB were achieved. All the results obtained show better performances when comparison was made with the conventional single-stage L-band optical amplifier.     

Generation of dual-wavelength domain-wall rectangular-shape pulses in HNLF-based fiber ring laser

The generation of dual-wavelength domain-wall rectangular-shape pulses in a highly nonlinear fiber (HNLF)-based fiber ring laser is experimentally demonstrated. The dual-wavelength lasing operation is realized by employing the intracavity birefringence-induced spectral filtering effect. An 85 m long HNLF is introduced into the fiber ring laser to enhance the nonlinear effect, which is favorable for the cross coupling between the two lasing beams. Experimentally, it was found that the interval of two domain walls in the time domain could be adjusted by simply tuning the linear cavity phase delay, which results in the achievement of different output pulse shapes. By properly rotating the polarization controller (PC), the dual-wavelength rectangular-shape pulses could be efficiently obtained. The proposed fiber laser provides a simple and efficient way to generate rectangular-shape pulse.     

Theory and experiment of flat-top all-fiber comb filter based on two high birefringence fiber Sagnac loop filters

A simple flat-top all-fiber comb filter based on two high birefringence fiber (HBF) Sagnac loop filters is presented. The proposed flat-top comb filter consists of two HBF Sagnac loop filters with two polarization controllers (PCs) and a fiber circulator. According to the theoretical analysis, with proper settings of the polarization state of the PCs, the comb filter can realize flat-top passband and the channel spacing also can be switched when the comb filter is convex spectrum. The 0.3 dB bandwidth of the flat-top passband is 0.49 nm with a free spectral range of 1.4 nm. The maximum extinction ratio is nearly 20 dB. The comb filter with switchable channel spacing can be obtained from 0.7 nm to 1.4 nm.     

High-power tunable Er,Yb ribbon fiber laser

A high-power Er,Yb double-clad ribbon fiber laser pumped by a 9-diode-bar pump module is reported. The laser yielded 102 W of continuous-wave output at 1566 nm for a launched pump power of 244 W, corresponding to a slope efficiency of ~ 44% with respect to launched pump power. Tunable operation was achieved using a simple external feedback cavity with a diffraction grating and the operating wavelength could be tuned from 1533 nm to 1567 nm. Temperature distribution in the ribbon fiber geometry and prospects of power scaling will be discussed.