High-power Er-Yb-doped fiber amplifier with multichannel gain flatness within 0.2 dB over 14 nm

A high-power Er-Yb fiber amplifier for WDM applications has been constructed using a matched mid-stage gain shaping filter. Using precise measurements and careful design considerations, excellent gain flatness, with less than 0.2-dB variation, was obtained over a 14-nm spectral bandwidth. By simply adjusting the pump power to the amplifier, it was possible to maintain the flattened amplifier gain shape over a wide input signal power range from -11 dBm to 1 dBm. A low external noise figure of 5.2 dB at 1-dBm signal input and a high-output power up to 24.6 dBm has been measured.     

All optical gain-locking in erbium-doped fiber amplifiers usingdouble-pass superfluorescence

All optical gain-locking in an erbium-doped fiber amplifier (EDFA) is demonstrated. A double-pass superfluorescence is created by using a broad-band fiber reflector centered at 1530 nm at the output of the EDFA, to lock the gain at 21 dB. Experiments on an eight-channel wavelength-division-multiplexing system shows promise with gain variation between channels of less than 0.6 dB over the input signal power range. While, gain variation with input signal power is about 0.2 dB for all channels     

High-gain polarization-insensitive optical amplifier

A polarization-insensitive optical amplifier (PIOA) consisting of two serial semiconductor laser amplifiers (SLAs) is studied theoretically and experimentally. A polarization-insensitive isolator (PII) inserted between the two SLAs serves not only to eliminate the coupling cavity, but also to rotate any polarized forward light by 90°. Experimental results show a maximum fiber-to-fiber gain of 29 dB. PIOA gain deviation for the input polarization launch angle is just 0.6 dB compared to an original value of 5-6 dB in a single SLA. A theoretical analysis shows that it is necessary to achieve a PII rotation design error of less than 0.5° in order to suppress deviation below 0.1 dB. PIOA noise figure deviation, for the input signal polarization launch angle, was only 0.1 dB from both the experimental and theoretical results even though there was a rotation error of 2°     

Precision measurement method for cryogenic amplifier noise temperatures below 5 K

We report precision measurements of the effective input noise temperature of a cryogenic (liquid-helium temperature) monolithic-microwave integrated-circuit amplifier at the amplifier reference planes within the cryostat. A method is given for characterizing and removing the effect of the transmission lines between the amplifier reference planes and the input and output connectors of the cryostat. In conjunction with careful noise measurements, this method enables us to measure amplifier noise temperatures below 5 K with an uncertainty of 0.3 K. The particular amplifier that was measured exhibits a noise temperature below 5.5 K from 1 to 11 GHz, attaining a minimum value of 2.3 K/spl plusmn/0.3 K at 7 GHz. This corresponds to a noise figure of 0.034 dB/spl plusmn/0.004 dB. The measured amplifier gain is between 33.4 dB/spl plusmn/0.3 dB and 35.8 dB/spl plusmn/0.3 dB over the 1-12-GHz range.     

An optical power equalizer based on one Er-doped fiber amplifier

A device which exhibits zero or slightly negative differential optical gain over a broad input power range is demonstrated. The scheme is based upon saturation enhancement by bidirectional signal input in an Er-doped fiber amplifier. Power equalization of better than 1.2 dB over a 14-dB dynamic input power range is achieved at the 1530-nm signal wavelength. The noise figure penalty due to the equalization is below 3 dB as evaluated by a device simulation     

Reduced intermodulation distortion in 1300 nm gain-clamped MQWlaser amplifiers

A 1300 nm gain-clamped DFB multiple quantum well laser amplifier with negligible pass band ripple, 20 dB fiber to fiber gain, and 10 dB reduction in gain saturation is demonstrated. The remaining gain saturation is attributed to longitudinal hole burning. After some modifications the reduction in gain saturation is improved to more than 30 dB for an input signal having the same polarization state as the lasing mode. From these experiments and a theoretical analysis it is concluded that there is a potential for realizing highly linear 1300 nm CATV semiconductor laser amplifiers using gain-clamping with less intermodulation distortion than today's directly modulated linear semiconductor lasers     

A high-performance monolithic IF amplifier incorporating electronic gain control

A direct-coupled monolithic IF amplifier that incorporates an active gain control stage and exhibits a power gain of 50 dB and an AGC range of 60 dB at 50 MHz is described. This circuit has negligible change in either input or output admittance, and has excellent signal linearity over the full range of gain control. Experimental and theoretical analyses are made of the large signal response, stability, available gain, and noise behavior of the circuit. An application to color television is discussed in which the functions of the 45-MHz IF amplifier and the dc-AGC circuitry are fabricated on a single die.     

A high-performance 2—18.5-GHz distributed amplifier—Theory and experiment

A high-performance 2-18.5-GHz monolithic GaAs MESFET distributed amplifier has been designed and fabricated. The distributed amplifier is analyzed theoretically using a normalized transmission matrix approach, and a closed-form gain equation is presented for the MMIC m-derived drain-line case. Theoretical predictions are compared to measured results and more complicated CAD models. The measured small, signal gain is typically 8.0±0.40 dB from 2-18.5 GHz at standard bias. Typical input return loss is greater than 12 dB, and the output return loss is greater than 15 dB. The saturated output power is in excess of 23 dBm over most of the band, and the noise figure is less than 7.5 dB.     

Polarization diversity detection performance of 2.5-Gb/s CPFSKregenerators intended for field use

2.5-Gb/s continuous-phase frequency-shift keying (CPFSK) regenerators are studied in laboratory and field experiments. A polarization diversity receiver is constructed with newly designed automatic gain and automatic frequency controllers. It achieves a sensitivity fluctuation of about 0.5 dB against all input signal polarization states. The automatic gain control is used in the intermediate-frequency circuits of the receiver and stably operates over 15 dB of input signal power variation. The automatic frequency control (AFC) is sufficiently stable to withstand a 30-kHz input signal polarization variation between two orthogonal linear polarization modes. AFC stability is maintained even if the environmental temperature of the laser diode modules fluctuates from 15 to 35 C. The polarization fluctuation in both cases results in only 0.1-dB degradation in receiver sensitivity     

A 77 GHz mHEMT MMIC Chip Set for Automotive Radar Systems

A monolithic microwave integrated circuit (MMIC) chip set consisting of a power amplifier, a driver amplifier, and a frequency doubler has been developed for automotive radar systems at 77 GHz. The chip set was fabricated using a 0.15 µm gate‐length InGaAs/InAlAs/GaAs metamorphic high electron mobility transistor (mHEMT) process based on a 4‐inch substrate. The power amplifier demonstrated a measured small signal gain of over 20 dB from 76 to 77 GHz with 15.5 dBm output power. The chip size is 2 mm × 2 mm. The driver amplifier exhibited a gain of 23 dB over a 76 to 77 GHz band with an output power of 13 dBm. The chip size is 2.1 mm × 2 mm. The frequency doubler achieved an output power of –6 dBm at 76.5 GHz with a conversion gain of ?16 dB for an input power of 10 dBm and a 38.25 GHz input frequency. The chip size is 1.2 mm × 1.2 mm. This MMIC chip set is suitable for the 77 GHz automotive radar systems and related applications in a W‐band.     

Dual wavelength pumped L- and U-band Raman amplifier

A Raman fibre amplifier providing small signal gain of over 30 dB in the U-band has been demonstrated. In addition, a dual wavelength pumped Raman amplifier with broad flattened gain (ripple better than 1.5 dB) over the spectral range 1600-1670 nm is presented     

A dual differential charge-coupled analog delay device

A dual differential charge-coupled analog device providing signal delays of 24 and 48 elements has been designed for sampled data analog signal processing applications. The aim of this design was to eliminate some of the disadvantages that have been associated with previous charge-coupled devices (CCD's). These include clock pickup, thermally generated dc offsets, and complex external control and amplification circuitry. The device has an input strobing circuit and an on-chip output amplifier. With a clock frequency of 8 kHz and a 400-mV rms input signal, the total harmonic distortion was below 0.2 percent and the signal-to-noise ratio was better than 70 dB with a 4-kHz bandwidth. The device gain was 6 dB and a gain variation of 0.2 dB was observed over a temperature range of 0 to 55°C.     

A dual differential charge-coupled analog delay device

A dual differential charge-coupled analog device providing signal delays of 24 and 48 elements has been designed for sampled data analog signal processing applications. The aim of this design was to eliminate some of the disadvantages that have been associated with previous charge-coupled devices (CCD's). These include clock pickup, thermally generated d.c. offsets, and complex external control and amplification circuitry. The device has an input strobing circuit and an on-chip output amplifier. With a clock frequency of 8 kHz and a 400-mV r.m.s. input signal, the total harmonic distortion was below 0.2 percent and the signal-to-noise ratio was better than 70 dB with a 4-kHz bandwidth. The device gain was 6 dB and a gain variation of 0.2 dB was observed over a temperature range of 0 to 55/spl deg/C.     

低压工作的轨到轨输入／输出缓冲级放大器

本文提出了一种低压工作的轨到轨输入／输出缓冲级放大器。利用电阻产生的输入共模电平移动,该放大器可以在低于传统轨到轨输入级所限制的最小电压下工作,并在整个输入共模电压范围内获得恒定的输入跨导;它的输出级由电流镜驱动,实现了轨到轨电压输出,具有较强的负载驱动能力。该放大器在CSMCO．6-μmCMOS数模混合工艺下进行了HSPICE仿真和流片测试,结果表明：当供电电压为5V,偏置电流为60uA,负载电容为10pF时,开环增益为87．7dB,功耗为579uw,单位增益带宽为3．3MHz;当该放大器作为缓冲级时,输入3VPP10kHz正弦信号,总谐波失真THD为53．2dB。     

Semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed systems

The fabrication and performance of a InGaAsP-InP semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed system is described. The amplifier is of the buried facet design and has polarization and reflectivity gain ripple of less than 1 dB. Using subcarrier multiplexing, multiple 50-Mb/s data streams at a wavelength of 1.553 /spl mu/m are infected into the amplifier. The gain nonlinearity of the amplifier transfers the data to a different wavelength of light simultaneously injected into the amplifier. Error free retrieval of subcarrier multiplexed data has been demonstrated for the wavelength converted output. The small signal bandwidth of the wavelength conversion process is 5 GHz. Calculation suggests that higher bandwidth is feasible at higher input powers at the expense of lower modulation transfer during wavelength conversion.     

Gain clamping in two-stage L-band EDFA using a broadband FBG

A gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) with an improved gain characteristic is demonstrated by simply adding a broadband conventional band (C-band) fiber Bragg grating (FBG) in a two-stage amplifier system. The FBG reflects backward C-band amplified spontaneous emission (ASE) from the second stage back into the system to clamp the gain. The gain is clamped at about 22.4 dB with a gain variation below 0.4 dB for input signal powers of -40 to -15 dBm. Compared with an unclamped amplifier of similar noise figure values, the small signal gain has improved by 2.4 dB due to the FBG which blocks the backward propagating ASE. At wavelengths from 1570 to 1600 nm, gain of the clamped amplifier varies from 19.4 to 26.7 dB. The corresponding noise figure varies by /spl plusmn/0.35 dB around 5 dB, which is not much different compared to that of the unclamped amplifier.     

A low-noise L-band EDFA with a 1500-nm Raman-pumped dispersion-compensating fiber section

This report presents a low-noise L-band erbium-doped fiber amplifier (EDFA) with a dispersion-compensating Raman amplifier. With an optimized prestage and 1500-nm Raman-pump laser diodes, the proposed EDFA achieved an internal noise figure of less than 4.5 dB over a 33-nm flat gain bandwidth within 0.5 dB at -2 dBm of large signal input power.     

L-band erbium-doped fibre amplifier with clamped- and flattened-gain using FBG

A gain clamped long wavelength band erbium-doped fibre amplifier (L-band EDFA) based on a ring laser cavity is demonstrated using a fibre Bragg grating (FBG) at the output end of the amplifier. This new design provides a good gain clamping as well as a gain flattening. The gain is clamped at 16.9 dB with gain variation of less than 0.1 dB from input signal power of -40 to -18 dBm by setting the VOA=5 dB. Also, the amplifier has the flattest gain spectrum at VOA=5. The gain variation is less than 1.0 dB within the wavelength range from 1570 to 1600 nm. This gain clamped amplifier also can support a 12 channel WDM system.     

High-gain, high-power 1550-nm polarization independent MQW optical amplifier

A practical 1550-nm polarization independent semiconductor optical amplifier configuration employing compressively strained quantum wells and a few commercially available optical components is reported. Crosstalk from counter propagating light, which may easily occur in such a configuration, has been sufficiently suppressed for practical use. For the entire configuration a net fiber-to-fiber gain of 17 dB, a 3-dB saturation output power of 13 dBm and a noise figure of 9 dB have been demonstrated. The polarization dependence was only 0.7 dB. The polarization independent 1550-nm semiconductor optical amplifier reported here is attractive when power consumption and compactness are of major concern and especially for applications involving nonlinear signal processing and switching.     

1.55-μm polarization-insensitive optical amplifier withstrain-balanced superlattice active layer

A polarization insensitive (sensitivity <1 dB) GaInAs-GaInAsP semiconductor optical amplifier has been realized at 1.55 μm. The active layer consists of a strain-balanced superlattice structure. Gain polarization insensitivity on a large bandwidth (60 nm) together with a 22.5-dB signal gain and a 11-dBm polarization-insensitive saturation output power are obtained