Monolithic DWDM source with precise channel spacing

We report a low-cost manufacturing approach for fabricating monolithic multi-wavelength sources for dense wavelength division multiplexing(DWDM)systems that offers high yield and eliminates crystal regrowth and selective area epitaxy steps that are essential in traditional fabrication methods.The source integrates an array of distributed feedback(DFB)lasers with a passive coupler and semiconductor optical amplifier(SOA).Ridge waveguide lasers with sampled Bragg side wall gratings have been integrated using quantum well intermixing to achieve a fully functional four-channel DWDM source with 0.8 nm wavelength spacing and residual errors<0.13 nm.The output power from the SOA is>10 mW per channel making the source suitable for use in passive optical networks(PONs).We have also investigated using multisection phase-shifted sampled gratings to both increase the effective grating coupling coefficient and precisely control the channel lasing wavelength spacing.An 8-channel DFB laser array with 100 GHz channel spacing was demonstrated using a sampled grating with twoπ-phase-shifted sections in each sampling period.The entire array was fabricated by only a single step of electron beam lithography.     

取样光栅的反射谱特性及其应用

本文基于取样光栅的独特反射谱特性,对其作为光子器件如DBR激光器、波分复用/解复器和光插分复用器的结构图作了探讨.通过比较得知,用取样光栅构成的新型光子学器件比用单纯的光纤光栅构成的光子学器件在未来的密集型波分复用(DWDM)光纤通信系统中更有实用价值.     

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.     

A gain-clamped SOA with distributed Bragg reflectors fabricated under both ends of active waveguide with different lengths

We demonstrate a gain-clamped semiconductor optical amplifier (GC-SOA) which has gratings under both end regions of an active waveguide. Two gratings of the new GC-SOA are fabricated in different lengths. Their lasing modes and gain characteristics are measured and analyzed with different combinations of grating lengths. It shows different gain and noise characteristics according to the measurement direction in asymmetric grating combinations.     

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.     

室温稳定多波长光纤激光器技术的研究新进展

室温稳定的多波长光纤激光器( MWFL)中最关键的技术是如何有效抑制掺杂光纤的均匀展宽效应。综述了国际上近年来提出的实现室温稳定多波长光纤激射的主要技术。介绍了近几年我们在该领域的一些创新性研究工作:提出了多种基于多谐振峰的光纤布拉格光栅(FBG) ,如多模光纤布拉格光栅、保偏光纤布拉格光栅、取样光纤布拉格光栅等的可开关多波长光纤激光器的新方法和新结构,实现了多种波长间隔小于2 nm,室温工作稳定性好、波长及波长间隔可调的可开关多波长光纤激光器;提出了基于非线性光纤环镜( NOLM)和非线性偏振旋转(NPR)效应的两种多波长掺铒光纤激光器(EDFL)实现技术,实现了室温稳定、功率谱分布平坦的宽带多波长激光输出,3 dB带宽内的波长个数可达50个,每个波长的功率波动在2 h内小于0 .1 dB。     

A unidirectional room temperature multi-wavelength fiber ring laser without isolator

A simplified ring cavity for achieving a unidirectional room temperature multi-wavelength erbium-doped fiber ring laser without optical isolator is demonstrated. The fiber ring cavity is built in such a way that the optical fields propagating in two directions suffer different losses caused by one sampled fiber Bragg grating. Furthermore, simultaneous multi-wavelength lasing with 0.8-nm intervals is demonstrated with sinusoidal phase modulation just before the sampled fiber Bragg grating to prevent single-wavelength lasing and unstable wavelength oscillation.     

Optical high-frequency pulse generation with wavelength tunability by using a DBR laser with vernier-type gratings

An optical high-frequency pulse generation method with wavelength tunability is presented by taking advantage of vernier-type gratings in a distributed Bragg reflector laser diode. Experimental results showed that sinusoidal optical pulses, whose lasing wavelengths were tunable, were created with repetition frequencies around 30 GHz. The widths of the radio frequency spectra, furthermore, were drastically reduced by means of mode locking with externally injected optical pulses.     

双环内级联采样光栅的多波长锁模光纤激光器

为了实现多波长激光输出,提出了一种改进的多波长主动锁模光纤环形激光器,采用集成级联采样光纤光栅进入激光腔形成稳定的多种波长激光的方法,进行了理论分析和实验验证。结果表明,双环形腔结构对于所有波长激光,其腔长度是一致的,从而可以用相同的锁模信号实现所有波长的同步锁模。实验中光纤环形激光器成功实现了以1.6nm为间隔的波长多达14个;它的输出功率大于0dBm,边模抑制比约30dB,最高模式锁模频率为1.05GHz,输出脉冲序列的脉宽是216ps。这一结果对光纤传输系统设计是有帮助的。     

Single-polarization generation in fiber Fabry-Perot laser byself-injection locking in short feedback cavity

Single-frequency and single-polarization lasing can be generated in a compact self-injection locked fiber Fabry-Perot laser with a short fiber Bragg grating feedback cavity. No discrete polarization control components are required. Different wavelengths actress the laser gain bandwidth can be generated by an appropriate combination of cavity designs and feedback fiber Bragg gratings. A 10-Gb/s nonreturn-to-zero transmission test demonstrates the laser's applicability for optical fiber communications     

External Cavity Lasers Composed of Higher Order Gratings and SLDs Integrated on PLC Platform

Very compact 4‐channel 200‐GHz‐spacing external cavity lasers (ECLs) were fabricated by hybrid integration of reflection gratings and superluminescent laser diodes on a planar lightwave circuit chip. The fifth‐order gratings as reflection gratings were formed using a conventional contact‐mask photo‐lithography process to achieve low‐cost fabrication. The lasing wavelength of the fabricated ECLs matched the ITU grid with an accuracy of ×0.1 nm, and optical powers were more than 0.4 mW at the injection current of 80 mA for all channels. The ECLs showed single mode operations with more than 30 dB side lobe suppression.     

Control of lasing wavelength in distributed feedback lasers byangling the active stripe with respect to the grating

We proposed and demonstrated a new and very simple technique of varying the lasing wavelength of distributed feedback (DFB) lasers with the need for fabricating gratings with different pitches. This is accomplished by angling the active stripe at an oblique angle with respect to the axis of the grating lines. This technique should be particularly suitable for fine tuning of lasing wavelength, and it eases the stringent demand on precise control of absolute grating pitches. It should be useful and important for dense (wavelength division multiplexing (WDM) applications and monolithic integration of multi-wavelength DFB lasers     

All-optical flip-flop based on coupled laser diodes

An all-optical set-reset flip-flop is presented that is based on two coupled lasers with separate cavities and lasing at different wavelengths. The lasers are coupled so that lasing in one of the lasers quenches lasing in the other laser. The flip-flop state is determined by the laser that is currently lasing. A rate-equation based model for the flip-flop is developed and used to obtain steady-state characteristics. Important properties of the system, such as the minimum coupling between lasers and the optical power required for switching, are derived from the model. These properties are primarily dependent on the laser mirror reflectivity, the inter-laser coupling, and the power emitted from one of the component lasers, affording the designer great control over the flip-flop properties. The flip-flop is experimentally demonstrated with two lasers constructed from identical semiconductor optical amplifiers (SOAs) and fiber Bragg gratings of different wavelengths. Good agreement between the theory and experiment is obtained. Furthermore, switching over a wide range of input wavelengths is shown; however, increased switching power is required for wavelengths far from the SOA gain peak     

Sub‐Micrometer Patterning of Amorphous‐ and β‐Phase in a Crosslinkable Poly(9,9‐dioctylfluorene): Dual‐Wavelength Lasing from a Mixed‐Morphology Device

The metastable β‐phase morphology, inherent to most polyfluorene homo‐polymers, is of interest due to its superior optical and electrical characteristics compared to its amorphous analogue. Here, a polyfluorene with vinyl‐ether‐functionalized aliphatic side‐chains that allow crosslinking is reported. It is demonstrated that the previously induced conformational morphology is preserved in the resulting polyfluorene network, which enables subsequent wet thin‐film processing. Electron‐beam lithography provides a means for sub‐(optical)‐wavelength patterning of the crosslinkable polyfluorene films. As a specific demonstration, optically‐pumped distributed‐feedback (DFB) lasers made from surface‐relief gratings in amorphous and β‐phase polyfluorene are presented. By backfilling gratings of one morphology by the other, devices are demonstrated that exhibit lasing at two wavelengths with a threshold (<1 μJ cm^?2) at least an order of magnitude lower compared with previous data.     

A Simple and Color-Free WDM-Passive Optical Network Using Spectrum-Sliced Fabry–PÉrot Laser Diodes

We propose and demonstrate a simple and color-free wavelength-division-multiplexing passive optical network (WDM-PON) using spectrum-sliced Fabry-Perot laser diodes (F-P LDs). Due to its low front facet reflectivity (~0.1%), the F-P LD shows a broadband lasing spectrum and reduced mode partition noise. By utilizing multiple peaks that are separated by the free-spectral range of the cyclic arrayed waveguide gratings, the 16-channel WDM-PON is successfully demonstrated at 155 Mb/s.     

Optical Arbitrary Waveform Generation Based on Sampled Fiber Bragg Gratings

Two approaches are proposed for generating optical arbitrary waveforms using sampled fiber Bragg gratings (FBGs). The manipulation of the optical spectrum of an input pulse is achieved by a sampled FBG which is fabricated using a novel technique based on the reconstruction-equivalent-chirp (REC) method. The key advantage of the REC technique is that it can produce FBGs with various phase profiles using a fabrication system having only micrometer precision. Two examples for the generation of Gaussian doublet pulses are demonstrated, which would find applications in ultra-wideband over fiber systems.     

基于氮化镓的通信波段可调DFB激光器的研究

为了利用悬空的周期可调光栅控制激光器的波长输出,采用了微机电系统技术中微驱动器与分布反馈激光器光栅相结合的结构,根据严格耦合波理论和介质平板波导理论,针对光通信的C波段,利用有限元软件COMSOL,建立了基于氮化镓的波长可调分布反馈激光器2维稳态模型。分析了1550nm处2维电场模式图以及激射波长线宽图,得到了激射波长与光栅周期的对应关系。结果表明,在光栅厚度、高度以及增益层厚度等结构参量一定的情况下,激射波长与光栅周期呈现与理论分析基本一致的似线性关系。该研究为该器件设计以及制备的后期工作开展提供了理论指导意义。     

Optical CDMA network codecs with merged-M-coded wavelength-hopping and prime-coded time-spreading

This paper proposes a new hybrid code for optical CDMA systems based on modified maximal-length sequence (M-sequence) codes for wavelength-hopping and prime codes for time spreading. Using the proposed hybrid code, two optical encoder/decoders are constructed using either fiber-Bragg gratings (FBGs) and optical delay lines, or arrayed-waveguide gratings (AWGs) and optical delay lines, respectively. The system performance is compared with that provided by the well-known prime-hop sequence code. The results show that the merged-M-sequence codes not only provide a higher capacity, but can also be realized via a simpler configuration. Furthermore, the proposed code is less expensive than prime-hop code under virtually identical BER conditions.     

Synthesized Structure of Amplitude—sampled FBG by Simple Inverse FT Technology and Its Application

Using the simple inverse Fourier transformation(FT), the index modulation structure with the sampled period for the sampled fiber Bragg gratings was designed. In this method, the enable channels are operated at identical wavelength while the unable channels are almost suppressed completely. The enable and unable channels can be established based on the applications. This technique is very useful to design the optical devices such as optical add and drop multiplexers (OADMs), and interleavers with dispersion and dispersion slope compensation.     

基于MZI和取样光栅的可调谐光分插复用器

提出一种基于马赫-曾德尔干涉仪(MZI)和取样光纤布拉格光栅(SFBG)的新型光分插复用器(OADM),它由两个并联马赫-曾德尔干涉仪和四个取样光纤布拉格光栅组成.对该光分插复用器的输出特性进行了理论仿真,研究得出通道间隔为0.8nm时下载和输出端口的光谱特性,研究发现干涉仪的臂长差和取样光栅的中心波长差是决定光分插复用器输出特性的主要因素.调节一个马赫-曾德尔干涉仪上的臂长差和取样光栅的中心波长,可以实现信号下载可调功能或直通功能.