Widely tunable ring-cavity tellurite fiber Raman laser

We report a widely tunable ring-cavity tellurite fiber Raman laser covering the S+C+L+U band. A tunable range (1495-1600 nm, limited by the tunable optical bandpass filter) over 100 nm is obtained by using a single-mode tellurite fiber with high Raman gain coefficients (55 W(-1)km(-1)) and large Raman shift (~22.3 THz) as the gain medium. Furthermore, the free-running 1665 nm Raman fiber laser is achieved from the ring cavity by removing the tunable optical bandpass filter, which shows that such a tellurite fiber has potential for constructing a widely tunable fiber Raman laser covering the S+C+L+U band. A high optical signal-to-noise ratio of over 60 dB for almost all of the tunable range is also demonstrated.     

Semiconductor optical amplifier-based laser with 25 km long cavity length utilizing sagnac fiber ring structure

In the investigation, we propose and demonstrate a Sagnac ring based fiber laser structure using a semiconductor optical amplifier (SOA) to act as a gain medium with short to long fiber cavity lengths for wavelength lasing and tuning. Here, ten fiber Bragg gratings (FBGs) with different reflected Bragg wave-lengths are used serving as the reflected element in the proposed laser configuration for wavelength lasing and remote sensing simultaneously. Furthermore, the different cavity fiber lengths of a few ten m to 25 km, which are used in the proposed laser scheme, has been analyzed and discussed.     

基于超长环形激光器泵浦的94 km布里渊分布式传感系统

首次将超长光纤环形激光器的光放大应用于布里渊光时域分析(BOTDA)传感系统,以延伸传感距离。 通过对布里渊泵浦消耗、 拉曼泵浦相对强度噪声(RIN)转移的抑制及拉曼泵浦功率分布的优化,基于对布里渊增益谱分析的原理在94 km的传感距离上实现了3 m空间分辨率,以及全程28 με/1.4 ℃应变/温度精度。     

一个新型的毫米波无线信号光纤传输系统及本振信号远程传送结构

摘要提出一个新型的毫米波光纤传输系统及本振信号远程传送的结构.此技术能为将来使用皮蜂窝网络提供宽带无线接入服务给出一个简单的基站接入点解决方案.计算和仿真结果表明,在激光器输出功率为－6.5 dBm,光放大增益为6 dB,激光线宽为1 MHz,75 MHz或150 MHz,误码率不超过10－9的情形下,622 Mbit/s的下行相移键控信号能够在传统单模光纤上传输超过30 km的距离.在具有相对大的激光器线宽150 MHz和光纤距离为30 km时,由激光器相位噪音和光纤色散所引起的（通过远程传送的）毫米波本振信号的额外相位误差的方差仅为1.74°.     

Random distributed feedback fiber laser pumped by an ytterbium doped fiber laser

A random distributed feedback fiber laser operating at 1115 nm has been demonstrated experimentally in standard communication optical fibers by using a LD-pumped Yb-doped fiber laser as the pump source. We have studied the effect of different fiber spans on this new type of random fiber laser output power. It is shown that the generation power is the highest up to 198 mW in a 50 km fiber span. The slope efficiency is more than 28.7%. Stable, high-power continuous-wave (CW) lasing can be generated when the pump power is 3.6 W. The threshold power has also been calculated which well proves a random fiber laser operating via Rayleigh scattering, amplified through the Raman scattering.     

Widely tunable linear-cavity multiwavelength fiber laser with distributed Brillouin scattering

We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration.The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end.Due to the weak reflectivity provided by the virtual mirror,self-lasing cavity modes are completely suppressed from the laser cavity.At Brillouin pump and 1480-nm pump powers of 2 and 130 mW,respectively,11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.     

Dispersion-tuned multiwavelength actively mode-locked fiber laser using a hybrid gain medium

We demonstrate a multiwavelength 10 GHz pulse source using a dispersion-tuned actively mode-locked fiber ring laser incorporated with a semiconductor optical amplifier and an erbium-doped fiber amplifier. Simultaneous seven-wavelength operation of the laser is obtained. The side-mode suppression of all wavelengths is above 30 dB. Smooth wavelength tuning is achieved over more than 12 nm by changing the modulation frequency or the length of the optical delay line. Pulse characteristics are almost constant over the entire tuning span. Wavelength spacing can also be varied from 0.9 to 10 nm by adjusting the dispersion of the cavity. These experimental observations agree well with theoretical analyses.     

Axial strain and temperature sensing characteristics of the single–coreless–single mode fiber structure-based fiber ring laser

This paper experimentally demonstrated a singlemode–coreless–singlemode (SCS) fiber structure-based fiber ring cavity laser for strain and temperature measurement. The basis of the sensing system is the multimodal interference occurs in coreless fiber, and the transmission spectrum is sensitive to the ambient perturbation. In this sensing system, the SCS fiber structure not only acts as the sensing head of the sensor but also the band-pass filter of the ring laser. Blue shift with strain sensitivity of \(\sim\) ?2 pm/με ranging from 0 to 730 με and red shift with temperature sensitivity of \(\sim\) 11 pm/°C ranging from 5 to 75 °C have been achieved. Experimental results also show the proposal has great potential in using long-distance operation. The fiber ring laser sensing system has a optical signal to noise ratio (OSNR) more than 50 and 3 dB bandwidth less than 0.05 nm. The result shows that the coreless fiber has no improvement of the temperature and axial strain sensitivity. However, compared to the common singlemode–multimode–singlemode fiber structure sensors, the laser sensing system has the additional advantages of high OSNR, high intensity and narrow 3 dB bandwidth, and thus improves the accuracy.     

Experimental Study of Four-Wave Mixing in Semiconductor Laser Amplifier and its Application to Dispersion Compensation in Mid-Span Spectral Inversion System

Properties of four-wave mixing (FWM) in the semiconductor laser amplifier are studied experimentally in this paper. The optical phase conjugation of the mixing wave is applied to compensate the chromatic dispersion of transmission fiber. It is presented experimental results of the transmission of short optical pulses with 12-ps width over 204 km standard single mode fiber. The results confirm that mid-span spectral inversion (MSSI) employing FWM in a semiconductor laser amplifier is one of potential dispersion compensation techniques for optical transmission over standard single mode fiber with bit rate beyond 40Gb/s.     

Experimental Study of Four Wave Mixing in Semiconductor Laser Amplifier and its Application to Dispersion Compensation in Mid Span Spectral Inversion System

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｔｈｅｍｉｄｓｐａｎｓｐｅｃｔｒａｌｉｎｖｅｒｓｉｏｎｅｍｐｌｏｙｉｎｇｆｏｕｒｗａｖｅｍｉｘｉｎｇｉｎａｓｅｍｉｃｏｎｄｕｃｔｏｒｌａｓｅｒａｍｐｌｉｆｉｅｒ（ＳＬＡ）ｉｓｏｎｅｏｆｔｈｅｐｏｔｅｎｔｉａｌｃｈｒｏｍ?..     

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser.     

Coherent transfer of an optical carrier over 251 km

We transfer an optical frequency over 251 km of optical fiber with a residual instability of 6x10(-19) at 100 s. This instability and the associated timing jitter are limited fundamentally by the noise on the optical fiber and the link length. We give a simple expression for calculating the achievable instability and jitter over a fiber link. Transfer of optical stability over this long distance requires a highly coherent optical source, provided here by a cw fiber laser locked to a high finesse optical cavity. A sufficient optical carrier signal is delivered to the remote fiber end by incorporating two-way, in-line erbium-doped fiber amplifiers to balance the 62 dB link loss.     

Using dual-mode self-locked semiconductor laser for optical millimeter-wave application

In this study, an optical millimeter-wave (mm-wave) generator is proposed and experimentally demonstrated by using a self-injected Fabry-Perot laser diode (FP-LD), having mode spacing of 1.11 nm, for dual-mode beating in 140 GHz band (terahertz band). The created dual-wavelength also can be also modulated at 1.25, 2.5, and 10 Gb/s with on-off keying (OOK) modulation format by external optical modulator, respectively, in 20 km fiber transmission. Moreover, the dual-mode laser can be selected in difference wave-lengths by tuning the optical filter inside cavity for the future WDM applications.     

Simulation of DWDM signals using optimum span scheme with cascaded optimized semiconductor optical amplifiers

We numerically simulated the ten channels at 10 Gb/s dense wavelength division multiplexing (DWDM) transmission faithfully over 17,227 km using 70 km span of single mode fiber (SMF) and dispersion compensating fiber (DCF) using optimum span scheme at channel spacing 20 GHz. For this purpose, inline optimized semiconductor optical amplifiers (SOAs) and DPSK format are used. We optimized the SOA parameters for inline amplifier with minimum crosstalk and amplified spontaneous emission noise with sufficient gain at bias current 400 mA. For this bias current, constant gain 36.5 dB is obtained up to saturation power 21.35 mW. We have also optimized the optical phase modulator bandwidth for 400 mA current which is around 5.5 GHz with crosstalk −14.2 dB between two channels at spacing 20 GHz.We show the 10×10 Gb/s transmission over 70 km distance with inline amplifier has good signal power received as compared to without amplifier, even at equal quality factor. We further investigated the optimum span scheme for 5670 km transmission distance for 10×10 Gb/s with channel spacing 20 at 5.5 GHz optical phase modulator bandwidth. As we increase the transmission distance up to 17,227 km, there is increase in power penalty with reasonable quality.The impact of optical power received and Q factor at 5670 and 17,227 km transmission distance for different span schemes for all channels has been illustrated. For launched optical power less than saturation, all channels are obtained at bit error rate floor of 10⁻¹⁰.     

Optimization of linear cavity design of Yb-doped double-clad fiber laser

The output characteristics of a linear cavity Yb-doped double-clad fiber (DCF) laser, including the effects of fiber length, fiber loss, and output mirror reflectivity on laser output power and threshold pump power have been studied theoretically and experimentally. In this paper, the linear cavity of double-clad fiber laser (DCFL) was composed of a pair of fiber Bragg gratings, while the facet of fiber was anti-reflection (AR) coated at 1070nm to erase the Fresnel reflection. Analysis showed that the laser output increases as the reflectivity of the fiber Bragg grating used as the output mirror decreases. At last, under the pump power of 14.4 W, single-mode laser output at 1070 nm was up to 10.8 W, with slope efficiency of 75 %.     

Long-distance fiber Bragg grating sensor system with a high optical signal-to-noise ratio based on a tunable fiber ring laser configuration

A novel tunable fiber ring laser configuration with a combination of bidirectional Raman amplification and dual erbium-doped fiber (EDF) amplification is proposed for realizing high optical signal-to-noise ratio (SNR), long-distance, quasi-distributed fiber Bragg grating (FBG) sensing systems with large capacities and low cost. The hybrid Raman-EDF amplification configuration arranged in the ring laser can enhance the optical SNR of FBG sensor signals significantly owing to the good combination of the high gain of the erbium-doped fiber amplifier (EDFA) and the low noise of the Raman amplification. Such a sensing system can support a large number of FBG sensors because of the use of a tunable fiber Fabry-Perot filter located within the ring laser and spatial division multiplexing for expansion of sensor channels. Experimental results show that an excellent optical SNR of approximately 60 dB has been achieved for a 50 km transmission distance with a low Raman pump power of approximately 170 mW at a wavelength of 1455 nm and a low EDFA pump power of approximately 40 mW at a wavelength of 980 nm, which is the highest optical SNR achieved so far for a 50 km long FBG sensor system, to our knowledge.     

Multi-wavelength Brillouin fiber laser generation using dual-pass approach

A simple and compact multi-wavelength tunable Brillouin fiber laser (BFL) in conjunction with dual-pass approach is proposed and experimentally compared with the output of a conventional single ring cavity architecture. This BFL source is demonstrated using 10 km long non-zero dispersion shifted fiber (NZ-DSF) as a Brillouin gain medium. By single ring cavity configuration, odd-order Brillouin Stokes lines appear in the backward direction with the line spacing 0.16 nm (∼20 GHz) between each two consecutive waves. However, this single ring cavity in conjunction with dual-pass configuration is able to generate Brillouin Stokes lines with 0.08 nm spacing by providing bi-directional oscillations of Brillouin waves in both forward and backward directions. With a Brillouin pump power of 15.3 dBm, approximately up to 17 Brillouin Stokes lines are generated which is tunable over 40 nm tuning range.     

Harmonic mode locking in a sliding-frequency fiber laser

We demonstrate a sliding-frequency mode-locked (SFM) erbium fiber laser generating 20 ps pulses with center wavelengths rapidly sweeping across a spectral range of 50 nm. Excess optical nonlinearity in the laser cavity leads to multipulsing, with a tendency to tight pulse bunching (<3 ns) at the fundamental cavity frequency of 25 MHz. The addition of a parallel optical delay line, with a path difference equal to a rational fraction of the cavity length, distributes the pulses uniformly across the entire cavity and achieves a harmonic SFM up to 1 GHz. The result establishes cavity nonlinearity as a critical design parameter for picosecond wavelength-swept lasers.     

Bi-directional dual-wavelength Brillouin lasing in a hybrid fiber ring cavity

In this paper, a novel Brillouin fiber laser (BFL) is proposed based on the hybrid fiber ring cavity composed of two types of fibers with different Brillouin shifts. Single mode fiber (SMF) and truewave fiber (TWF) are used in our experiments. Bi-directional dual-wavelength Brillouin lasing is achieved in the hybrid fiber ring cavity. The lasing lights along the two directions come from the Stokes waves generated in the two fibers, respectively, with different Brillouin shifts, however, they share the same fiber ring cavity. The BFL based on the hybrid fiber ring cavity provides a simple possible way to realize Brillouin fiber optical gyroscopes (BFOGs) without lock-in effect.     

Monolithically integrated chirp-managed laser based on a resonant tunneling filter

We have proposed a monolithically integrated chirp-managed laser (CML) that consists of a directly modulated single-mode DFB laser and an optical spectrum reshaper (OSR) filter based on a double-slanted-trench resonant tunneling structure (DST-RTS). Slanted trenches facilitates the occurrence of resonant tunneling effect, which produces a steep-edge narrow-band OSR filter, and meanwhile directing most of the reflected waves out of the laser cavity, consequently eliminating the need of an isolator. Characteristics of the DST-RTS filter have been investigated and simulation results show that the proposed 25 Gbps 1.55 μm CML can send signal over 22 km standard single-mode fiber for bit error rate of 10^?12.