Polarization-insensitive fiber optical parametric amplifier based on polarization diversity technique with dual parallel pumps

By analyzing the principle of dual-pump parametric amplification and the polarization dependent gain of fiber optical parametric amplifier(FOPA),a polarization-insensitive FOPA based on polarization-diversity technique with dual parallel pumps is presented.The performances of polarization-insensitivity,gain and BER are theoretically analyzed and numerically simulated by comparing the proposed scheme with parallel pump solution and orthogonal pump solution.The presented solution can reduce the complexity of state of polarization(SoP) of pumps.     

Multiwavelength generation in an erbium-doped fiber laser using in-fiber comb filters

Simultaneous continuous wave multiwavelength operation of an erbium-doped fiber laser has been demonstrated using two types of recently developed in-fiber grating comb filters. The lasing wavelengths and linewidths were determined by the comb filter, which was inserted in a ring cavity with a single inhomogeneously broadened gain medium.     

Gain characteristics of a dual-pump fiber optical parametric amplifier with Raman effect

We investigate the pump-depleted model of a dual-pump fiber optical parametric amplifier(FOPA) with Raman effect.As bandwidth increases,the gain profile of the distorted FOPA would be impacted seriously.Under the widebands,especially when the pump separation is large,zero dispersion wavelength(ZDW) fluctuation is another factor which can not be neglected.Numerical simulations with these comprehensive factors are mainly analyzed to obtain their influence on gain characteristics.Saturated gain spectrum is also discussed in detail.     

Multiwavelength fiber ring laser source based on a delayed interferometer

A multiwavelength fiber laser source is demonstrated with a semiconductor optical amplifier as the gain medium. A delayed interferometer is incorporated in the ring cavity serving as a comb-like multichannel filter. A stable 75-wavelength simultaneous operation spaced at 40 GHz with the extinction ratio of 40 dB is achieved. By tuning the cavity loss, the center wavelength of the generated lasing waveband could be varied by as much as 20 nm.     

工作在L波段的多波长Er3 /Yb3 共掺光纤激光器

采用Er^3 ／Yb^3 共掺双包层光纤(EYDF)作为增益介质，利用一段标准的多模光纤作为空间梳状滤波器，于室温下实现了5个波长的稳定输出。通过调节偏振控制器的状态，可以实现对波长振荡个数和波长间隔的控制。腔中不加任何的稳定装置，在激光输出功率高于207mw时，仍能够得到多波长的稳定振荡，单一波长的线宽窄于0．15nm，边模抑制比大于32dB。通过优化单模光纤与多模光纤的熔接，选择更加合适的多模光纤，可实现更多波长个数的稳定的多波长输出。     

Single-longitudinal-mode multiwavelength fiber ring laser

A single-longitudinal-mode multiwavelength fiber ring laser is proposed and demonstrated. The single-longitudinal-mode operation is realized using a fiber loop mirror with a saturable absorber. The fiber loop mirror acts as a passive self-tracking narrow multiband optical filter. Single-longitudinal-mode multiwavelength lasing is generated by using either a Lyot-Sagnac filter or a fiber grating array.     

Wavelength switching of a fiber laser with a Sagnac loop reflector

A multiwavelength fiber laser is constructed with an elliptical core erbium-doped fiber serving as an anisotropic gain medium. A broadband fiber reflector and a Sagnac loop reflector form a Fabry-Perot resonant cavity. Three lasing wavelengths are obtained which are stable over an hour at room temperatures. With one of them as reference wavelength, we can switch the other two by a polarization controller. The lasing wavelengths are also tunable. The effects of the anisotropic gain behavior of the erbium-doped fiber are also explored.     

掺镱光纤激光器的多波长振荡特性

利用Sagnac梳状滤波器,研究了环形腔掺镱光纤激光器(YDFL)在室温和77 K时的多波长振荡行为。结果表明,在室温和77 K时,掺镱光纤(YDF)均呈现明显的非均匀加宽效应,使得掺镱光纤激光器的起振波长数随抽运光功率的提高而增多。但在室温下,因均匀加宽效应强,掺镱光纤增益的非均匀加宽并不能补偿其内禀不平坦的增益谱,造成波长缺失现象,且当波长间隔减小至0.8 nm时,均匀加宽效应引起的波长竞争造成了多波长振荡的稳定性下降。而在77 K时,掺镱光纤非均匀加宽效应明显增强,在0.8 nm的波长间隔下,无波长缺失现象,将起振波长数增加到32个,且多波长振荡稳定。     

Multiwavelength laser source using linear optical amplifier

We propose and demonstrate a high-performance multiwavelength ring laser based on a linear optical amplifier (LOA) for potential applications in dense wavelength-division-multiplexing communication systems. Experimental results indicate that the inhomogeneous gain medium provided by the LOA reduces the gain competition and leads to stable multiwavelength lasing. Thirty-eight wavelengths covering C+L-band with 0.8-nm channel spacing are generated at room temperature. Simultaneous tuning of multiwavelengths is demonstrated and a stability test shows a power fluctuation of less than 0.2 dB during a 3-h test.     

Noise characteristics of dual-pump fiber-optic parametric amplifiers

The noise figure (NF) properties of an undepleted and lossless dual-pump fiber-optic parametric amplifier (FOPA) are theoretically and numerically investigated. The theoretical study takes into account the noise characteristics of the two pump waves that are considered to have parallel polarization states for gain maximization. It is shown that noisy pump waves degrade the amplifier's NF, especially when the amplifier is operating at high gain values and when the input signal is high. The theoretical observations are validated by Monte Carlo numerical simulations, and the agreement between them is excellent. Finally, a comparative study concerning the noise characteristics of dual-pump and single-pump FOPAs is performed.     

Behavioral Investigations of an Erbium-Doped Fiber Ring Laser through Numerical Simulations

An erbium-doped fiber ring laser is modeled, using the standard propagation and rate equations of a homogeneous, two-level medium. The numerical model has been obtained by developing a spectral analysis of erbium-doped fiber amplifiers. This approach is modified to account for the cyclical propagation of the field in the ring laser. The numerical simulations provide interesting information on the spectral behavior as well as important characteristics of the cavity, mainly the lasing wavelength and output power. The model also permits the study of competing modes' gain evolution during the transient state of a ring laser cavity, which enables cavity lasing wavelength predictions. To our knowledge, this study is the first of its kind.     

Lasing wavelength and spacing switchable multiwavelength fiber laser from 1510 to 1620 nm

We experimentally demonstrate a flexibly switchable multiwavelength fiber laser with multiple functionalities like a wide tuning range of lasing wavelength, wavelength spacing, and the number of channels simultaneously. The lasing wavelength is controlled in the range from 1510 to 1620 nm based on the effect of nonlinear gain compression of a semiconductor optical amplifier incorporated with an erbium-doped fiber amplifier. The wavelength spacing and the number of channels in the multiwavelength fiber laser are readily controlled by the effective length of polarization-maintaining fiber (PMF) segments in the intracavity PMF Lyot-Sagnac filter.     

Bidirectional 10-GHz optical comb generation with an intracavityfiber DFB pumped Brillouin/erbium fiber laser

We present multiwavelength and bidirectional operation of a novel Brillouin/erbium fiber ring laser. Multiwavelength operation is seeded by an Er³⁺:Yb³⁺ fiber distributed-feedback (DFB) laser inserted into the ring cavity. We realized lasing at up to eight wavelengths separated by 10.6 GHz     

Multiwavelength actively mode-locked fiber laser with a double-ring configuration and integrated cascaded sampled fiber Bragg gratings

A modified multiwavelength actively mode-locked fiber ring laser is proposed and experimentally demonstrated. In this kind of laser, stable multiwavelengths lasing is achieved by integrating cascaded sampled fiber Bragg gratings (SFBGs) into the laser cavity. To implement actively mode-locking technique, a double-ring cavity configuration is used to assure that the cavity lengths for all wavelengths lasing are identical. Thus, simultaneous mode locking of all wavelengths has been successfully achieved by using same mode-locking signal.     

Multiwavelength Erbium-Doped Fiber Laser Employing Cavity Loss Modulation

A novel and simple multiwavelength erbium-doped fiber laser is proposed and demonstrated. The combination of a polarization scrambler and a polarizer is employed to induce polarization-dependent-loss modulation. The loss modulation induced multiwavelength lasing by alleviating the mode competition caused by homogeneous gain broadening of the erbium-doped fiber. As a result, 11-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved. The output power distribution is quite uniform and the power fluctuation of each wavelength is smaller than 0.6 dB.     

Multiwavelength Actively Mode-locked Fiber Laser with a Double-ring Configuration and Integrated Cascaded Sampled Fiber Bragg Gratings

A modified multiwavelength actively mode-locked fiber ring laser is proposed and experimentally demonstrated. In this kind of laser, stable multiwavelengths lasing is achieved by integrating cascaded sampled fiber Bragg gratings（SFBGs） into the laser cavity. To implement actively mode-locking technique, a doublering cavity configuration is used to assure that the cavity lengths for all wavelengths lasing are identical. Thus, simultaneous mode locking of all wavelengths has been successfully achieved by using the same mode-locking signal.     

Multiwavelength lasers based on semiconductor optical amplifiers

Stable multiwavelength lasing is demonstrated with a novel laser, in which a semiconductor optical amplifier offers optical gain and cascaded sampled fiber gratings serve as a comb filter. Five lasing lines are obtained with a fixed wavelength spacing of 0.8 nm. Optical power fluctuations among the lasing lines are improved by adjusting the reflectivity profile through the cascade of two sampled gratings     

Multiwavelength erbium-doped fiber ring laser employing Fabry–Perot etalon inside cavity operating in room temperature

In this investigation, we propose and demonstrate a simple and cost-effective erbium-doped fiber (EDF) ring laser using a Fabry–Perot etalon inside a linear cavity and employing the accurate fiber cavity length to satisfy the least common multiple number for generating multiwavelength in C-band at room temperature. Furthermore, the center wavelength of the lasing wavelength bands can be adjusted to 1541.02, 1551.32, and 1562.03 nm, respectively. The wavelength separation in each wavelength band is 0.34 nm. Moreover, the output stability of the multiwavelength laser has also been discussed and analyzed.     

Multiwavelength erbium-doped fiber lasers with active overlapping linear cavities

Multiwavelength oscillations in erbium-doped fiber (EDF) lasers with active overlapping linear cavities are investigated in detail. The laser can be designed to produce multiwavelength oscillations in the C-band and in the L-band. With a C-band three-wavelength laser, experiments show that the output powers of the lasing lines increase linearly or piecewise linearly with pump input. Any one lasing wavelength can be tuned over several nanometers depending on the gain tilt in the vicinity of the lasing wavelength while multiwavelength oscillation is still being maintained. The output power of any specific lasing line can be adjusted by suitably designing the EDF sections. This property also allows the laser to operate in multiwavelength switching mode. The laser exhibits a novel multiwavelength optical bistable behavior in the L-band. With an L-band dual-wavelength laser, the bistable input-output hysteresis behaviors of the two L-band wavelengths evolve in antiphase with respect to each other. The width of the bistable region has been increased to several tens of mW. It can be controlled and adjusted by the cavity loss and the EDF length. It is found that simultaneous L-band dual-wavelength oscillations can be obtained when part of the EDF, which functions as a saturable absorber, has been bleached. Moreover, simultaneous multiwavelength oscillations in both C-band and L-band have also been successfully demonstrated with the laser.     

Photonics True-Time-Delay Unit for Phased-Array Antenna Using Multiwavelength Fiber Laser Based on a Sagnac Interferemetric Filter

A photonics true-time-delay system for phased array beamforming using a chirped grating-based time-delay element and a novel multiwavelength erbium-doped fiber ring laser source employing a Sagnac filtering mirror is proposed. The Sagnac filtering mirror consists of a polarization maintaining directional coupler and two pieces of polarization maintaining fibers. The lasing wavelength and number are determined by properly adjusting the polarization controller within the unidirectional ring cavity and are very stable. A chirped-grating-based true-time-delay system using the proposed laser source is constructed and demonstrated experimentally.