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.     

Tunable multi-wavelength fiber laser based on a polarization-maintaining erbium-doped fiber and a polarization controller

A stable and tunable multi-wavelength fiber laser with a polarization-maintaining erbium-doped fiber (PM-EDF) and a polarization controller (PC) is proposed and demonstrated. A homemade PM-EDF incorporated in the ring cavity is used as the gain medium. Simultaneous multi-wavelength oscillation is achieved at room temperature. The theory of the PM-EDF and PC to suppress the wavelength competition is described in detail. The 3 dB bandwidth is less than 0.01 nm. The power fluctuation and wavelength shift are measured to be less than 0.5 dB and 0.05 nm over 32 min. The wavelength tuning between single-, double-, triple-, and four-wavelength is realized.     

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.     

Advanced multifunctional optical switch for multimode optical fiber networks

In this work, an advanced multifunctional optical switch based on multimode fibers is proposed. It can work as a 3 × 1 optical multiplexer/combiner, a 2 × 2 optical switch, a variable optical attenuator and a variable optical power splitter. All these functionalities can be developed in the same device without any hardware modification, only by using the proper ports and control electronics.The proposed switch has been developed for being used in the visible and near infrared wavelength range: 450–650 nm for optical fiber automobile applications, 650–850 nm for home broadband applications; and 850–1300 nm for multimode fiber access networks. Up to three different types of twisted nematic liquid crystal cells have been designed and fabricated for fulfilling these different wavelength ranges as part of the proposed device.The multifunctional switch has been implemented and experimentally tested. Crosstalk usually better than ? 15 dB at 532 nm, 660 nm and 850 nm, in any state has been measured. Switching is achieved at voltage levels of 4 Vrms. Fiber to fiber insertion losses when operating as a 2 × 2 optical switch, range from 10 to 15 dB within 200 nm wavelength range; with a non-optimized optics for collimation and coupling.     

A novel triple pump 1050 nm, 1400 nm, 800 nm pumping scheme for thulium doped fiber amplifier

Thulium doped fiber amplifier is a good candidate for S, and S+ band. This paper demonstrated a three pump pumping scheme for thulium doped fiber amplifier with 1050 nm co propagating pump and 1400 nm and 800 nm counter propagating pumps with a total pumping power 600 mW. This configuration yields up to 33 dB gain in 20 nm region from 1460 nm to 1480 nm, with noise figure <4 dB. To the knowledge of authors it is the highest gain achieved by thulium-doped amplifier in a single pass configuration with good power conversion efficiency.     

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.     

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.     

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%.     

Low-threshold all-fiber 1000 nm supercontinuum source based on highly non-linear fiber

We present an highly efficient all-fiber compact supercontinuum source that exhibits a nearly flat spectrum from 1.1 μm to 2.1 μm. This broadband infrared optical source is made-up of a highly non-linear fiber pumped by a 1.55 μm self-Q-switched Er-Brillouin nanosecond pulsed fiber laser, which in turn is pumped by a low-power 1480 nm laser diode. In this work we highlight the great potential of highly non-linear fiber for supercontinuum generation with respect to conventional dispersion-shifted fiber by demonstrating a significant 10 dB power enhancement in the short wavelength side of the supercontinuum.     

Multiwavelength fiber ring laser using a gain clamped semiconductor optical amplifier

We demonstrate a novel multi-wavelength fiber ring laser based on a gain clamped semiconductor optical amplifier. The number of lasing lines can be tuned by adjusting the loss inside the cavity. The wavelength interval between the wavelengths is 100 GHz. The proposed laser shows a stable operation with total intensity fluctuation for a single laser line within ±0.02 dB at room temperature for a period of 30-minutes.     

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.     

PbS quantum dot fiber amplifier based on a tapered SMF fiber

A PbS quantum dot coated (QD-coated) tapered fiber amplifier with a broad bandwidth is theoretically demonstrated. The QD layer is coated on the surface of a tapered fiber and is excited by the evanescent wave of a pump. An optical gain of 10.5 dB, with a 160-nm broad bandwidth of at 1530-nm center wavelength, is achieved. The gain efficiency is over 4 dB/cm. This QD-tapered fiber amplifier has a concentration control of the QDs, a lower insertion loss, and shows good suppression of amplified spontaneous emission (ASE), while its structure is also quite simple. Therefore, the proposed fiber amplifier has great potential in fiber-optic communication systems.     

Dual-wavelength narrow-linewidth fiber laser based on F-P fiber ring filter

A dual-wavelength fiber laser with a narrow-linewidth, based on a P-F fiber filter has been proposed. Polarization-maintaining fiber Bragg grating (PM-FBG) and a F-P fiber filter are introduced based on the traditional fiber laser. PM-FBG is used as the wavelength selection device. The fiber F-P filter consists of two optical couplers and a section of un-pumped erbium-doped fiber (EDF). Due to the delay of cavity and the loss generated by the EDF, the filter has comb spectral response. The incorporation of the fiber F-P filter leads to the suppression of undesirable modes. At the room temperature, under 980 nm LD pumped, the maximum output of the two wavelengths is respectively ?2.259 dBm and 0.568 dBm, with the 3-dB bandwidth separately 0.1 nm and 0.14 nm, realizing the narrow linewidth and dual-wavelength output.     

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.     

56 dB Gain EYDFA with improved noise figure with dual-stage partial double pass configuration

An efficient erbium/ytterbium co-doped fiber amplifier (EYDFA) is demonstrated by using a dual-stage partial double pass structure with a band pass filter (BPF). The amplifier achieves the maximum small signal gain of 56 dB and the corresponding noise figure of 4.66 dB at 1536 nm with an input signal power and total pump power of ?50 dBm and 140 mW, respectively. Compared with a conventional single-stage amplifier, the maximum gain enhancement of 16.99 dB is obtained at 1544 nm with the corresponding noise figure is improved by 2 dB. The proposed amplifier structure only uses a single pump source with a partial double pass scheme to provide a high gain and dual-stage structure to provide the low noise figure.     

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.     

Numerical analysis of a broadband spectrum generated in a standard fiber by noise-like pulses from a passively mode-locked fiber laser

This paper covers a numerical analysis of supercontinuum spectrum generation in a piece of standard fiber by using as the pump noise-like pulses produced by a passively mode-locked fiber laser. An experimental study was also carried out, yielding results that support the numerical results. In the numerical study we estimated that the spectral extension of the generated supercontinuum reaches ~ 1000 nm, and that it presents a high flatness over a region of ~ 220 nm (1630 nm-1850 nm) when we use as the pump noise-like pulses with a wide optical bandwidth (~ 50 nm) and a peak power of ~ 2 kW. Experimentally, the output signal spectrum extends from ~ 1530 nm to at least 1750 nm and presents a high flatness over a region of 1640 nm to 1750 nm for the same value of numerical input power, 1750 nm being the upper limit of the optical spectrum analyzer. The numerical analysis presented here is thus an essential part to overcome the severe limitation in measuring capabilities and to understand the phenomena of supercontinuum generation, which is mainly related to Raman self-frequency shift. Finally, this work demonstrates the potential of noise-like pulses from a passively mode-locked fiber laser for broadband spectrum generation.     

Supercontinuum broadening in all-normal dispersion photonic crystal fiber by means of soliton compression in standard single-mode fiber

Using standard single-mode fiber as high-order soliton compressor for broadening supercontinuum in an 80 m long all-normal dispersion photonic crystal fiber is investigated experimentally and numerically. An analytical formula for calculating proper fiber input power to generate the broadest supercontinuum is derived. The numerical results show that the formula is more accurate in high power level corresponding to the soliton order which is larger than two. The measured supercontinuum ? 20 dB bandwidth is broadened from 84.2 nm to 277.1 nm by using a 20 m long standard single-mode fiber without enhancing fiber input power. Numerical calculations of the amplitude noise in the output spectra show that using soliton compression effect can efficiently broaden the spectral bandwidth and not generate obvious noises.     

Adjustable EDFA gain equalization filter for DWDM channels based on a single LPG excited by flexural acoustic waves

A fast adjustable gain equalization filter for dense wavelength division multiplexing (DWDM) system is reported. The method is based on a single long period fiber grating (LPG) which is excited by means of flexural acoustic waves. The equalization of a typical erbium doped fiber amplifier (EDFA) gain spectrum with a gain flatness of <0.3 dB over a 32 nm bandwidth is demonstrated. The filter adjustment is obtained by choosing different acoustic loads applied to the acousto-optic modulator, which presents a switching time of ～17 μs. A maximum power penalty of 0.84 dB, relatively to the back-to-back signal, was achieved.