Multiwavelength-switchable SOA-fibre ring laser using sampled Hi-Bi fibre grating

A novel multiwavelength-switchable laser based on a semiconductor optical amplifier (SOA) within a fibre ring cavity with a sampled high-birefringence fibre grating is proposed. Four channels with 0.8 nm spacing have been generated at room temperature and switched to other channels with 0.4 nm wavelength-shift by adjusting an inserted polariser. The laser can be used in hierarchical cross-connect WDM networks employing an interleaved waveband concept.     

Multiwavelength erbium-doped fiber ring laser incorporating an SOA-based phase Modulator

A novel room-temperature multiwavelength erbium-doped fiber (EDF) laser is demonstrated. Stable multiwavelength lasing at room temperature is realized by incorporating a semiconductor optical amplifier (SOA)-based phase modulator in the laser cavity. The SOA is biased below the transparent point with a sinusoidal signal applied to achieve phase modulation, to suppress the homogenous line broadening of the EDF. Stable multiwavelength lasing with wavelengths up to 26 and wavelength spacing as small as 0.19 nm is demonstrated at room temperature.     

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.     

Multiwavelength all-fiber ring laser using side-polished fiber comb filter and mechanically formed long-period fiber gratings

Multiwavelength all-fiber lasers to be operated at room temperature are demonstrated. A side-polished fiber comb filter and mechanically formed long-period fiber gratings (LPFGs) are used to generate colasing operation. By using the band suppression characteristics of the LPFGs to prevent the gain cross-saturation effect, simultaneous lasing of four-wavelength peaks is obtained.     

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.     

Multiwavelength pulse generation using an actively mode-locked erbium-doped fiber ring laser based on distributed dispersion cavity

A simple design of a stable multiwavelength pulse generator was demonstrated using a dispersion-tuned actively mode-locked erbium-doped fiber (EDF) ring laser with distributed dispersion cavity. The distributed dispersion cavity in the fiber laser successfully reduced the cross-gain saturation in EDF, and thus, enabled multiwavelength operation. Simultaneous generation of wavelength-tunable 10-GHz pulses up to four different wavelengths was achieved with the same wavelength space of 2.94 nm. The extinction ratio of all wavelengths was above 30 dB. In addition, smooth wavelength tuning was achieved over more than 41 nm when the laser was working at dual-wavelength mode. The super mode noise was /spl sim/60 dB below the signal level at both wavelengths. The laser state was found to be very stable.     

Multiwavelength sources using laser diodes frequency-locked toatomic resonances

It is shown that low-cost compact disk AlGaAs laser diodes make it possible to realize manifold optical sources with precise and stable wavelengths when locked to rubidium vapor resonances. Many optical frequency references can be obtained with the use of absorption cells containing a foreign gas or by placing cells in static magnetic fields. The same approach can be used with other wavelengths required by optical fiber communications     

All-optical switch based on digital micromirrors

A dynamic 1 /spl times/ 4 all-optical switch based on digital mirror arrays is described and analyzed. A total insertion loss of -5.5 dB, crosstalk of less than -36.8 dB, and bit-error rates of less than 10/sup -12/ have been measured at 2.5 Gb/s. The performance of the switch in multiwavelength applications to variable optical attenuator and multicasting is described.     

Multiwavelength tunable fiber ring laser based on sampled chirp fiber Bragg grating

We propose and experimentally demonstrate a novel configuration of a multiwavelength tunable fiber ring laser with equally increased or decreased wavelength spacing. Wavelength tuning is achieved by tuning the strain gradient of a sampled chirp fiber Bragg grating (SCFBG), which is integrated in the laser cavity. To achieve equally increased or decreased wavelength spacing, the SCFBG is surface-mounted at a slant onto one lateral side of a plate so that each wavelength-selective element of the SCFBG will experience an equal strain increment when an external force is applied to the plate. We experimentally obtain seven lasing wavelengths with equally increased or decreased wavelength spacing.     

A switchable and tunable ytterbium-doped fiber ring laser with a Sagnac loop mirror

A switchable and tunable ytterbium-doped fiber ring laser(YDFL) is reported and demonstrated. Employing a Sagnac loop mirror fabricated by an 85-cm-long polarization-maintaining fiber(PMF), the proposed YDFL can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1 064 nm. Both stable dual-wavelength lasing and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the proposed fiber laser with two different operation modes is rather stable at room temperature.     

Multiwavelength birefringent-cavity mode-locked fibre laser

Generation of simultaneous four wavelength optical pulses is successfully demonstrated using a novel multiwavelength mode-locked Er/sup 3+/-doped fibre ring laser with two, 45 degrees concatenated, birefringent fibres in the cavity. Wavelength separations of 0.9-2.7 nm and pulse durations of 28-55 ps are obtained.<>     

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.     

三波长自由切换激光系统

针对工程应用中对多波长激光源的使用需求,提出了一种可自由切换三种波长输出的激光系统。高稳定、高光束质量抽运源通过由电光晶体和偏振分光棱镜组成的波长切换装置,实现首次波长切换;光参量振荡器输出的闲频光和信号光通过由机械调控的光学陷阱实现二次波长切换;再采用光路折叠和合束镜多波段镀膜技术,最终实现共光路三波长激光自由切换输出。当抽运功率为14 W时,信号光和闲频光功率超过5 W,光光转换效率为35.9 %。三种激光的输出功率不稳定度均小于2 %。两次波长切换都可在全温度范围内进行,能量关闭程度接近100 %,切换速度分别为纳秒级和毫秒级。经过监测,系统能够长时间稳定工作,具备工程应用能力。     

Wavelength add-drop switching using tilting micromirrors

This paper describes a single-mode optical fiber switch which routes individual signals into and out of a wavelength multiplexed data stream without interrupting the remaining channels. The switch uses free-space optical wavelength multiplexing and a column of micromechanical tilt-mirrors to switch 16 channels at 200 GHz spacing from 1531 to 1556 nm. The electrostatically actuated tilt mirrors use an 80 V peak-to-peak 300 KHz sinusoidal drive signal to switch between ±10° with a 20 μs response. The total fiber-to-fiber insertion loss for the packaged switch is 5 dB for the passed signals and 8 dB for added and dropped signals, with 0.2 dB polarization dependence. Switching contrast was 30 dB or more for all 16 channels and all input and output states. We demonstrate operation by switching 622 Mb/s data on eight wavelength channels between the two input and output ports with negligible eye closure     

Multiwavelength picosecond optical pulse generation using anactively mode-locked multichannel grating cavity laser

A multichannel grating cavity (MGC) InGaAsP-InP ridge diode laser is found to be suitable for multiwavelength ultrashort optical pulse generation using active mode-locking techniques. By using different configurations of the MGC laser, dual wavelength picosecond pulses are successfully produced with good spectral quality, either simultaneously or with a programmable relative delay between the channels. For a channel separation of 2.2 nm, pulses with a duration of 60 ps and a spectral width of 11.6 GHz have been obtained. The experimental results are compared with those from a theoretical analysis of the multiwavelength mode-locking process using a set of modified coupled-cavity rate equations. The minimum achievable pulsewidths generated by the actively mode-locked MGC laser are shown to be limited by the resolution bandwidth of grating used. The dependence of pulsewidth on RF drive frequency detuning is examined and it is found that the ultrashort pulses can be obtained over a wide range of frequency detuning. The interchannel cross-talk originating from gain saturation and carrier depletion is also discussed     

A switchable dual-wavelength erbium-doped fiber laser based on saturable absorber and active optical fiber ring filter

We propose a specific aspheric cylindrical optical system to transform Gaussian beam to flat-top and rectangular beam. The Gaussian beam shaping system is composed of dual orthogonal aspheric cylindrical lenses. The principle of shaping Gaussian beam is studied theoretically. The mapping function of arbitrary rays in an incident plane and an image plane is deduced based on the law of energy conservation, and the real ray tracing method is adopted to design the shaping system. Finally, the lens system is processed by single point diamond turning techniques. Testing results indicate that the system achieves the theoretical expectation, and the uniformity of flat-top and rectangular beam is 88.2%. The method is not only simple but also practical.     

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 grating reflectors for widely tunable laser

We propose a new reflector approach in order to get the reflectivity comb needed in widely tunable lasers. This reflector is realized by holographic exposure of superimposed multiple Bragg gratings. It provides efficient reflectivity with short guide sections (150 /spl mu/m) leading to improved static laser characteristics. This reflector has been successfully included in 20-nm tuning DBR lasers.