Compensation of Raman-induced crosstalk using a lumpedgermanosilicate fiber Raman amplifier in the 1.571-1.591-μm region

A new method to equalize power imbalance caused by Raman-induced crosstalk among optical channels is proposed using a lumped germanosilicate fiber Raman amplifier. Evolution of optical channels through the Raman amplifier was simulated using Raman frequency modeling, which theoretically predicted simultaneous amplification and power equalization. Experimentally, a gain band with negative slope in the range of 1.571-1.591 μm was achieved in a lumped Raman amplifier pumped by a broad-band laser diode centered at 1.467 μm. We demonstrated compensation of the Raman-induced crosstalk of 5 dB accumulated along 330 km of conventional single-mode fiber     

Nd-doped double-clad fiber amplifier at 1.06 μm

We propose and demonstrate a double-clad neodymium (Nd)-doped fiber amplifier (IVDFA) at 1.06 μm for a compact configuration of a high-power optical amplifier. The proposed 125 μm first cladding diameter in the double-clad fiber, provides the single-mode propagation of the signal lightwave into its doped core without misguiding the signal lightwave into the outer core (first cladding), by simply splicing with a standard single-mode fiber. Furthermore a fiber grating in a single-mode core of the double-clad fiber allows the double-pass configuration for the signal lightwave at 1.06 μm and also allows the pump lightwave coupling at 0.81 μm into the first cladding without employing a bulk dichroic mirror. We demonstrate the signal output power of 110 mW for a 550-mW pump input from a multimode fiber coupled pump source. Theoretical results predict an efficient high-power operation of the amplifier by improving the signal scattering loss in the double-clad fiber     

2-Gbit/s signal amplification at λ=1.53 μm in anerbium-doped single-mode fiber amplifier

The gain, saturation power, and noise of an erbium-doped single-mode traveling-wave fiber amplifier operating at a wavelength λ=1.53 μm are characterized. In continuous-wave (CW) measurements amplification at 2 Gbit/s was demonstrated with up to 17-dB gain for 1×10^-9 bit error rate at 1.531 μm and a 3-dB full bandwidth of 14 nm. From the determination of the fiber-amplifier's output signal-to-noise ratio versus input signal power during data transmission, it was concluded that, with signal levels used here, signal-spontaneous beat noise limited the receiver sensitivity improvement. With the fiber amplifier acting as an optical preamplifier of the receiver, the best sensitivity was -30 dBm, obtained after installing a polarizer at the fiber amplifier output to reject half of the applied spontaneous emission power. This sensitivity was 6 dB better than without the fiber amplifier, proving that the fiber amplifier can be used as a preamplifier     

Upconversion pumped thulium-doped fluoride fiber amplifier andlaser operating at 1.47 μm

A 1.064-μm band upconversion pumped Tm³⁺-doped fluoride fiber amplifier and a laser both operating at 1.47 μm are investigated in detail. The two devices are based on the ³F ₄→³H₄ transition in a trivalent thulium ion, which is a self-terminating system. When pumped at 1.064 μm, the amplifier has a gain of over 10 dB from 1.44 to 1.51 μm and a low-noise characteristic. Also, the fiber laser generates a high-output power of over 100 mW with a slope efficiency of 59% at around 1.47 μm. These levels of performance will be important for optical communication systems     

1.3-μm Pr-doped In-Ga-based fluoride fiber amplifiers pumped bygrating-fiber-pigtailed 0.98-μm-band laser diodes with a detunedwavelength of 1 μm

At most efficient pump wavelength, a praseodymium-doped In-Ga-based fluoride fiber is directly pumped by four 0.98-μm-band laser diodes. These lasing wavelengths are detuned from 0.98 to 1 μm by external selective optical feedback from fiber grating reflectors. Maximum signal output power of +13.5 dBm is obtained at 1.296 μm. Four-wavelength multiplexed signals at 1.296-1.311 μm are amplified with a deviation of gain less than 1.9 dB. By using the amplifier as a power booster, data of 2.5 Gb/s is successfully transmitted more than 100 km     

Analysis of optical gain enhanced erbium-doped fiber amplifiersusing optical filters

Erbium-doped fiber amplifiers (EDFAs) with enhanced optical gain obtained by incorporating narrow-bandpass optical filters into the amplifier length are studied. It is shown in theory that it is possible to increase optical gain by more than 10 dB for optical signals around the wavelength of 1.55 μm, compared with conventional EDFAs without filters. It is also shown that the gain improvement at longer wavelengths away from the amplifier gain peak is much higher than that of the EDFA with an optical isolator within the amplifier length. The optimum filter position is found to be around 42% of the total amplifier length from the input end. The effects of filter insertion loss and pump loss are discussed. This amplifier can be used as an optical preamplifier in a receiver for a wide range of wavelengths     

28.3 dB gain 1.3 μm-band Pr-doped fluoride fiber amplifiermodule pumped by 1.017 μm InGaAs-LD's

A praseodymium (Pr)-doped fluoride fiber amplifier (PDFA) module that is pumped by strained quantum-well InGaAs laser diodes (LDs) is described. The amplifier module, consisting of a four LD pump configuration and a high NA Pr-doped fluoride fiber with low scattering loss, exhibits a maximum signal gain of 28.3 dB and a saturation output power of 6 dBm at a signal wavelength of 1.30 μm. It is shown to be the most promising module for the 1.3-μm-band optical amplifier     

Solid-state laser pumping of 1.5-μm optical amplifiers andsources for lightwave video transmission

An optical power amplifier and a laser source are demonstrated at 1.5 μm. A diode-pumped Nd:YAG laser is used as the pumping source for an Er/Yb co-doped gain medium. The power scaling advantages of this approach are demonstrated. Up to +21 dBm of output power is obtained from the Er/Yb amplifier and up to +19 dBm is obtained from the laser source. The Er/Yb power amplifier was deployed in a 42-channel AM link with 40 km of fiber, and an optical loss budget of 18 dBm was demonstrated     

Femtosecond soliton transmission characteristics in an ultralongerbium-doped fiber amplifier with different pumping configurations

The transmission characteristics of femtosecond optical solitons in an 18.2 km-long erbium-doped fiber amplifier (EDFA) have been investigated in detail by changing the pumping configuration. With backward pumping, a lossless transmission of 440 fs solitons at 1.55 μm has been realized with a pump power of 16 mW. The output pulsewidth is determined by the spectrum modified by the soliton self-frequency shift. In a bidirectional pumping configuration, 440-fs soliton pulses have been transmitted for a total pump power of 38 mW, where the output pulse width is determined by the original 1.55 μm spectrum. Although a femtosecond soliton is very weakly trapped in the EDFA-gain bandwidth of 1.55 μm and the soliton self-frequency shift inevitably occurs, the femtosecond pulse component still exists at 1.55 μm, and a pulse can be successfully transmitted with a gain of 11 dB and very little pulse broadening     

Wide-range all-optical wavelength conversion usingdual-wavelength-pumped fiber Raman converter

A wavelength conversion scheme based on a fiber Raman converter is proposed, in which an externally injected high power pump laser and the associated Stokes laser are used to assist the Raman conversion process of signal light coded with optical information. Because the Raman gain spectrum in fibers is extremely broad, a wavelength conversion device with wide-range tunability is feasible. We numerically demonstrate that wavelength conversion from 1.31 to 1.42 μm can be realized using a fiber Raman converter at up to 10 Gb/s with an efficiency of 18%. It is also demonstrated that wide range conversion from 1.31 to 1.55 μm for optical fiber communication is feasible at up to 5 Gb/s when the fiber Raman converters are cascaded twice     

多泵浦增益平坦光子晶体拉曼光纤放大器

针对密集波分复用光纤通信系统中拉曼光纤放大器增益及增益谱平坦问题,提出一种采用4个泵浦光的多泵浦方式在光子晶体光纤不同位置处注入两种不同波长泵浦光的组合方式来获得拉曼光纤放大器增益更大、增益谱更加平坦的方法。这种组合方式在拉曼光纤放大器中使得光信号实现了前段放大、后段补偿,从而在拉曼光纤放大器输出端获得高增益和较平坦增益谱。模拟的结果表明:平均增益可达:26.5 dB,增益平坦度为0.046 dB。     

An optical fiber amplifier for wide-band wavelength range around1.65 μm

The optical amplification characteristics of a 0.781-μm pumped thulium-doped fiber in the wavelength range of 1.6-1.7 μm are discussed. A maximum net gain of 2.0 dB was obtained for 1.69-μm operation. This optical fiber amplifier is suitable for in-service monitoring and identifying fibers operating at 1.2-1.6 μm     

Application of an Er3+-doped fibre amplifier to an OTDRoperating at 1.6 μm

An erbium-doped fibre amplifier with a high gain coefficient at 1.6 μm is constructed employing a dual pumping scheme. The amplifier is successfully applied to an OTDR, producing output optical pulses characterised by a peak power of 476 mW for a duration of 1 μs     

Efficient optical amplifier using a low-concentration erbium-dopedfiber

A gain coefficient of 3.8 dB/mW was achieved for an erbium-doped fiber amplifier pumped by a 1.48 μm laser diode. The main reasons for the improvement are high NA (0.23) and low concentration (43 p.p.m.). Pump-to-signal energy conversion efficiency was 18% at 3 dB gain compression. A decrease in saturation power with increasing erbium concentration was also demonstrated. In high-concentration fiber, fluorescence at 0.98 μm due to cooperative upconversion was detected. These results indicate that several kilometers of distributed fiber amplifier with high gain and high output saturation power could be possible, because the absorption coefficient at 1.48 μm is still two orders higher than the background loss in the 43 p.p.m. fiber     

Experimental studies on wavelength division bidirectional opticalamplifiers using an Er3+-doped fiber

This paper presents a novel structure of an Er³⁺-doped fiber amplifier capable of bidirectional operation through the wavelength division multiplex method. The idea is to combine an Er³⁺-doped fiber, pump devices, optical isolators, and wavelength selective couplers so that two lightwaves having different wavelengths pass each proper isolator. The suitable structure was determined from experimental studies on several basic amplifier configurations. Optical gains of more than 25 dB were attained in both wavelength regions of 1.533 μm and 1.55 μm. Successful bidirectional operation of the amplifier was confirmed by means of a 2.488-Gbit/s-signal transmission experiment     

Diode-array pumping of Er3+/Yb3+ Co-dopedfiber lasers and amplifiers

Single-mode double-clad Er³⁺/Yb³⁺ co-doped fibers are shown to be suitable for diode array pumping at around 960 nm. A fiber laser with 96-W output power at 1.53 μm and a power amplifier exhibiting a small signal gain of 24 dB and a saturated output power of +17 dBm are reported     

Multichannel AM-VSB television signal transmission using anerbium-doped optical fiber power amplifier

The use of an erbium-doped optical fiber power amplifier in a multichannel amplitude-modulated vestigial-sideband CATV transmission system for potential subscriber loop applications is discussed. Using a color-center laser pump at 1.48 μm, a fiber-to-fiber gain of 11.5 dB (at 1.539 μm), which is 10 dB compressed from the small-signal gain, and a total system power margin of 15 dB were achieved. No intermodulation distortion was introduced by the fiber amplifier. The received video SNR of 40-46 dB was limited by the linearity of the distributed-feedback laser diode used     

An automatic-gain-controlled Raman fiber amplifier/gain-clamped SOA for metro WDM networks with changes in span loss

We propose an automatic-gain-controlled Raman fiber amplifier/gain-clamped semiconductor optical amplifier. The amplifier uses a feedforward gain-control scheme to maintain the channel output power. The signal power after the optical amplifier is automatically controlled to within 0.15 dB when the span loss changes from 16 to 26 dB.     

Praseodymium-doped fiber amplifiers: theory of 1.3 μm operation

A theoretical model of optical amplification in a praseodymium-doped fiber amplifier that is optically pumped at about 1 μm and amplifies signals at about 1.3 μm is presented. The variation of gain with respect to fiber length in both small-signal and saturated operation is reported, and the adverse influences of a lower-level bottleneck and a multiphonon cascade from the pump band are discussed     

A 1.5-V high drive capability CMOS op-amp

A novel CMOS operational amplifier with a 1.5 V power supply is presented. It is based on a folded-mirror transconductance amplifier and a high-efficiency output stage. The amplifier achieves an open-loop gain and a gain-bandwidth product higher than 65 dB and 1 MHz, respectively. In addition, a 1 V peak-to-peak output voltage into a 500 Ω and 50 pF output load is provided with a total harmonic distortion of -77 dB. This performance was achieved using maximum aspect ratios of 120/1.2 and 360/1.2 for the NMOS and PMOS transistors, respectively, and a quiescent current as low as 60 μA for the driver transistors. The amplifier was implemented in a standard 1.2 μm CMOS process with threshold voltages around 0.8 V. It dissipates less than 300 μW