82-channel multi-wavelength comb generation in a SOA fiber ring laser

We demonstrate a multi-wavelength semiconductor optical amplifier (SOA) fiber ring laser with a dual-pass Mach-Zehnder interferometer (MZI) filter. Two SOAs with different gain spectra provide sufficient gain and a wider gain spectrum to facilitate multi-wavelength lasing. The dual-pass MZI, configured by adding an optical isolator to the two outputs of the conventional MZI, serves as comb filter for multi-wavelength operation, and its extinction ratio can be enhanced to twofold as that of the conventional MZI in the same parameters. To investigate the influences of a dual-pass MZI filter and a conventional MZI filter on multi-wavelength operation, two different cavity configurations are presented and compared, including a single-SOA ring cavity and a double-SOA ring cavity. Stable simultaneous operation at 82 wavelengths, with a wavelength spacing of 40 GHz and a power deviation of 5 dB, and with a minimum optical signal-to-noise ratio (OSNR) of 28 dB, is observed from the double-SOA ring cavity using a dual-pass MZI filter.     

Tunable 19 × 10 GHz L-band FP-SOA based multi-wavelength mode-locked fiber laser

We present a multi-wavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a Fabry-Perot semiconductor optical amplifier (FP-SOA). Because the gain of the SOA is depleted by an external injection optical signal, the SOA acts as a loss modulator. The FP-SOA serves as a tunable comb filter. The presented laser source can generate 19 synchronized wavelength channels with the extinction ratio of about 21 dB, each mode-locked at 10 GHz, and mode-locked pulse width is about 40 ps. Oscillation wavelengths band can be tuned by adjusting the bias current of the SOA, and wavelength spacing also can be changed by using a tunable optical delay line (ODL) or a temperature controller. The polarization-insensitive devices ensure that the output power is rather stable. This fiber laser has potential applications in longer waveband (L-band) within the low-attenuation window.     

Dual-cavity dual-output multi-wavelength fiber laser based on nonlinear polarization rotation effect

We demonstrate a multi-wavelength fiber laser based on nonlinear polarization rotation (NPR) in dual-cavity configuration with two output ports. The laser employs a piece of erbium doped fiber (EDF) and semiconductor optical amplifier (SOA) as the gain medium in a separate cavity. By incorporating PCF in the dual cavity the non-linear polarization rotation (NPR) effect is enhanced and thus higher output and more oscillating lasing can be achieved. The laser produces three strong lines with a spacing of 2.40 nm and side mode suppression ratio (SMSR) of more than 10 dB at 1535 nm region. Another output produces 8 lines of optical comb with a spacing of 0.54 at 1570 nm region.     

基于半导体光放大器的可调谐多波长光纤激光器

报道了一种新型环形腔可调谐多波长光纤激光器,腔内以半导体光放大器为增益介质,利用高双折射光纤构成的高双折射环形镜的滤波特性,在室温下,获得了基本符合ITU-T标准100GHz的17个波长以上的稳定多波长输出.各信道峰值功率差小于6 dB,线宽小于0.102 nm,信噪比大于25 dB.通过调节高双折射环形镜内的偏振控制器状态实现了这一组波长整体在50GHz范围内连续可调谐.并利用实验方法,对该光纤激光器应用于掺铒光纤放大器对多信道放大性能测试的可行性进行了初步探讨.     

Tunable multi-wavelength fiber ring laser based on a Hi-Bi fiber loop mirror

A novel tunable multi-wavelength fiber ring laser based on semiconductor optical amplifier(SOA)is proposed by using a high-birefringence(Hi-Bi)fiber loop mirror(FLM)as wavelength filter.With this configuration,the wavelength spacing of this laser can be varied by using the different lengths of Hi-Bi fiber.8 wavelengths spacing on 450 GHz are experimentally obtained with more than 25-dB signal-to-noise ratio(SNR)for each channel using 1.28-m Hi-Bi fiber in Hi-Bi FLM.The output power variation between different channels is measured to be less than 5.9 dB.The linewidth of each channel is compressed from 0.347 to 0.186 nm by 1.5-m unpumped erbium-doped fiber(EDF).Meanwhile,17 wavelengths spacing on ITU-gird(100 GHz)are also obtained with 5.9-m Hi-Bi fiber in Hi-Bi FLM.All these channels can be tuned together over 0.4 nm.     

Multi-wavelength fiber source with equal frequency spacing

A optical filter based on Sagnac interferometer was proposed to be acted as a comb filter with equal frequency spacing and good signal to noise ratio (SNR), which was composed of an 8.14 m stress-induced Hi-Bi (high-birefringence) PM (polarization-maintaining) fiber. Using this multi-wavelength Sagnac comb filter and a gain flattening Sagnac filter that made the output spectra flattening at different pump powers, a 25-channel multi-wavelength all-fiber source were successfully generated with channel spacing of 0.8 nm with respect to the center wavelength at 1550 nm and flattened gain about ±1 dB peak deviation. The channel spacing can be further reduced to 0.4 nm to produce a DWDM (dense wavelength division multiplexing) source, simply by increasing the Hi-Bi fiber to be 16.28 m. It can be used in many applications such as WDM (wavelength division multiplexing), optical amplifiers with a high SNR, narrow band filters and optical sensors.     

Analysis of polarization-independent tunable optical comb filter by cascading MZI and phase modulating Sagnac loop

A novel scheme of tunable optical comb filter constructed by cascading a polarization-swapping MZI and a phase modulating Sagnac loop is proposed. The key features of this comb filter design are its polarization-independence and high speed in wavelength tuning. The wavelength tunability can be readily achieved by incorporating an electro-optic phase modulator into the Sagnac loop. In addition, the filter can be made amplitude adjustable as well. The filter will be desirable for multi-wavelength fiber lasers, multi-channel optical signal processing and optical WDM systems.     

Tunable 12×10 GHz mode-locked semiconductor fiber laser incorporating a Mach-Zehnder interferometer filter

A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10 GHz, pulse width of mode-locked pulse are about 30 ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as simple and compact structure, easy integration, convenient tuning, good stability, potential high repetition rate operating, which has potential application in the future WDM communication system.     

Waveband switchable multi-wavelength erbium-doped fiber ring laser based on wavelength-dependent polarization rotation mechanism

A waveband switchable multi-wavelength erbium-doped fiber ring laser based on wavelength-dependent polarization rotation mechanism and birefringence-based in-line comb filter is proposed and demonstrated. The two lasing wavebands, around 1530 and 1560 nm region, can be efficiently switched by simply rotating the polarization controllers (PCs). The channel spacing is 0.4 nm which was determined by the length of polarization maintain fiber (PMF) used in the experiment. The experimental results show that the waveband switchable is an intrinsic feature of multi-wavelength fiber ring lasers by incorporating a passive polarizer in the laser cavity.     

SOA-Based Multi-Wavelength Laser Sources

We present recent advances in multi-wavelength, power-equalized laser sources that incorporate a semiconductor optical amplifier (SOA) and simple optical filters, such as Lyot-type and Fabry-Perot, for comb generation. Both linear and ring-cavity configurations are presented, and single-pass optical feedback technique is proposed to improve the performance in terms of the number of simultaneously oscillating lines and output channel power equalization. This technique resulted in a broadened oscillating spectrum of 52 lines spaced at 50 GHz, power-equalized within 0.3 dB. Finally, a simplified version that uses only an uncoated SOA for both gain and comb generation is demonstrated.     

Flexibly switchable multi-wavelength fiber optical parametric oscillator based on a Lyot-Sagnac filter

We experimentally demonstrate a flexibly switchable multi-wavelength fiber optical parametric oscillator (MW-FOPO) by employing a highly nonlinear dispersion-shifted fiber (HNL-DSF) as the gain medium and a Lyot-Sagnac fiber ring as the comb filter. The wavelength spacing and the number of channels in the switchable MW-FOPO are adjustable by controlling the effective length of polarization maintaining fiber (PMF) segments in the intracavity Lyot-Sagnac filter. We achieve 36 lasing channels with 0.5 nm-spacing and 22 lasing channels with 0.8 nm-spacing in a wavelength range from 1541 to 1559 nm at room temperature. A comparison of the output spectra between the dual-pump MW-FOPO and single-pump MW-FOPO is presented as well.     

Stable multiwavelength fiber ring laser with equalized power spectrum based on a semiconductor optical amplifier

We experimentally demonstrated a new structure of a multiwavelength semiconductor optical amplifier (SOA) ring laser based on a fiber Sagnac loop filter that can generate up to 25 stable output lasing wavelengths at room temperature. By varying the length of a polarization-maintaining (PM) fiber within the Sagnac loop filter, the wavelength spacing between the output lasing wavelengths can be changed to a desired value. By tuning a polarization controller (PC) within the Sagnac loop filter, stable multiwavelength 1550-nm operation with up to 17 lasing lines within 3 dB power level variation and with a wavelength spacing of ∼0.8 nm was achieved. The optical signal-to-noise ratios (OSNRs) of all the lasing wavelengths are greater than 40 dB.     

An Enhanced Bismuth-Based Brillouin/Erbium Fiber Laser with Linear Cavity Configuration

A multi-wavelength Brillouin/erbium-doped fiber laser (BEFL) which operates in 1594 nm region is demonstrated using a 215 cm long Bismuth-based EDF and SMF. Two optical circulators were used at the output ends of the system to form a linear cavity to produce a cascaded Brillouin Stokes and anti-Stokes. A stable output laser comb of more than 20 lines was obtained with a spacing of approximately 0.089 nm at a Brillouin pump power of 4 dBm and two 1,480-nm pumps at powers of 100 mW. The number of lines is relatively higher compared with the ring cavity BEFL.     

基于SOA和级联取样光纤光栅的多波长激光器

研究了基于半导体光放大器(SOA)和双段级联取样光纤光栅构成的新型结构多波长激光器.设 计了取样光纤光栅，计算了其反射谱，模拟了多波长激光器的输出光谱.基于自行制作的SOA 和取样光纤光栅，进行了多波长激光器的实验研究，得到了间隔为0.8nm、输出功率不平坦 度小于1.0dB的11个波长输出.理论和实验两个方面都可以验证：与基于普通取样光栅的多波 长方案相比，基于双段级联取样光栅的方案能改善输出谱平坦度，并可提高可激射波长数. 关键词： 半导体光放大器 取样光纤光栅 多波长激光器     

Multi-wavelength fiber laser based on nonlinear polarization rotation in semiconductor optical amplifier and photonic crystal fiber

A nonlinear polarisation rotation (NPR) based multi-wavelength laser source is demonstrated using a semiconductor optical amplifier (SOA) and photonic crystal fiber (PCF). The SOA acts as not only the gain medium but also the phase retarder for multi-wavelength oscillation in conjunction with an isolator. The incorporation of PCF improves the NPR effect and thus assists in the multiwavelength generation. The wavelength spacing reduces from 4.82 to 2.76 nm as the PCF length increases from 50 to 100 m. With a 100 m long PCF, the proposed laser produces at least 42 lasing wavelengths with optical signal to noise ratio of more than 10 dB.     

Multi-wavelength generation using a bismuth-based EDF and Brillouin effect in a linear cavity configuration

The generation of a multiple wavelength source using a bismuth-based erbium-doped fiber (Bi-EDF) in a linear cavity configuration is demonstrated. The configuration uses a pair of optical circulators at the input and output ends of the cavity to form a resonator for multi-wavelength generation in conjunction with optical couplers to inject the Brillouin pump (BP) and to tap the output at the two ends. The Brillouin erbium fiber laser (BEFL) comb with a 2.15 m of Bi-EDF has a wavelength spacing of 0.09 nm and operates in long-wavelength (L-) band region. A stable output laser comb of 50 lines is obtained at a BP of 1568.2 nm and 5 dBm and two 1480 nm pumps at 120 mW. The injected BP wavelength and power as well as the 1480 nm pump powers have a great effect on the number of lines and output power of the BEFL. This configuration is compact due to the use of the significantly shorter Bi-EDF as the linear gain medium, and can be made more compact by replacing the single-mode fiber with highly non-linear fibers such as holey fibers.     

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.     

基于半导体光放大器的非归零信号时钟恢复

提出了一种基于半导体光放大器加窄带光纤光栅滤波器,将非归零信号转换为伪归零信号,再把伪归零信号注入到主动锁模环行腔激光器进行时钟提取的非归零信号时钟恢复方案.利用该方案实现了10 Gb/s伪随机非归零信号的全光时钟恢复,对工作原理和结果进行了分析和讨论.实验证明该方案具有结构简单,调整容易,输出波形好的特点.     

多波长混沌掺铒光纤环形激光器实验研究

利用掺铒光纤环形激光器(EDFRL),基于光纤的非线性克尔效应,实验实现了多波长混沌激光输出。实验研究了EDFRL在时序上通过倍周期进入混沌的路径,并进行了理论分析,理论研究与实验结果一致。实验结果表明,随着抽运功率的增加,其光谱的输出呈现多波长,激光器最多可输出5个不同波长的混沌激光。采用光纤光栅进行滤波后,各个波长的输出均呈现混沌状态。     

Comparisons of multi-wavelength oscillations using Sagnac loop mirror and Mach-Zehnder interferometer for ytterbium doped fiber lasers

A multiwavelength Ytterbium-doped fiber ring laser operating at 1030 nm region is demonstrated using a Sagnac loop mirror and a Mach-Zehnder interferometer. We report the Performance comparisons of multi-wavelength oscillations in Yb³⁺ doped fiber lasers (YDFL) with typical commercial ytterbium doped silica fibers. By adjusting the polarization controller (PC), a widely tunable laser range of 22 nm from 1030 nm to 1050 nm is obtained. The Mach-Zehnder interferometer (MZI) design has exhibited simplicity in the operation for controlling the smallest wavelength spacing compared to Sagnac loop mirror method. In our observations, the smallest achieved stable wavelength spacing in Sagnac loop mirror setup and MZI setup were 2.1 nm and 0.7 nm, respectively. In case of nine-wavelength operation with a MZI setup, the stability, Full Width at Half Maximum (FWHM) and side mode suppression ratio (SMSR) of laser lines are not affected by increasing pump power, While for above four wavelength operation, the laser stability with Sagnac loop mirror becomes worse specially for higher input pump power and the power fluctuation among the wave-lengths would be also slightly larger.