A low power high linearity baseband for a direct conversation CMMB tuner

An analog baseband circuit made in a 0.35-μm SiGe BiCMOS process is presented for China Multimedia Mobile Broadcasting (CMMB) direct conversion receivers. A high linearity 8th-order Chebyshev low pass filter (LPF) with accurate calibration system is used. Measurement results show that the filter provides 0.5-dB passband ripple, 4% bandwidth accuracy, and -35-dB attenuation at 6 MHz with a cutoff frequency of 4 MHz. The current steering type variable gain amplifier (VGA) achieves more than 40-dB gain range with excellent temperature compensation. This tuner baseband achieves an OIP3 of 25.5 dBm, dissipates 16.4 mA under a 2.8-V supply and occupies 1.1 mm2 of die size.     

Design and performance evaluation of narrowband rectangular optical filter based on stimulated Brillouin scattering in fiber

We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in fiber with tunable bandwidth from 50 MHz to 4 GHz at 15-MHz tuning resolution. The steep-edged rectangular shape of the filter is precisely controlled utilizing digital feedback compensation of the multi-tone pump light. The passband ripple is \(\sim \)1 dB by nonlinearity management of the pump light and using the fiber with a single Brillouin peak. The filter selectivity is improved to more than 40 dB by using pump-splitting dual-stage configuration. We analyze the noise performance of the proposed SBS filter and demonstrate a sub-band extraction of a multi-band orthogonal frequency division multiplexing (OFDM) signal. Furthermore, we validate the amplification performance with different gains for OFDM signal, which shows the potential capability of the filter in the fields of optical signal processing.     

A 2.7-V 1.8-GHz fourth-order tunable LC bandpass filter based on emulation of magnetically coupled resonators

A low-voltage fourth-order RF bandpass filter structure based on emulation of two magnetically coupled resonators is presented. A unique feature of the proposed architecture is using electric coupling to emulate the effect of the coupled inductors, thus providing bandwidth tuning with small passband ripple. Each resonator is built using on-chip spiral inductors and accumulation-mode pMOS capacitors to provide center frequency tuning. The filter has been implemented in HP 0.5-/spl mu/m CMOS process and occupies an area of 0.15 mm/sup 2/. It consumes 16 mA from a single 2.7-V supply at a center frequency of 1.84 GHz and a bandwidth of 80 MHz while providing a passband gain of 9 dB and more than 30 dB of image attenuation for an IF frequency of 100 MHz. The measured output 1-dB compression point and output noise power spectral densities are -16 dBm and -137 dBm/Hz, respectively. This results in a 1-dB compression dynamic range of 42 dB. The filter minimum power supply voltage for proper operation is 2 V. The chip experimental results are in good agreement with theoretical results.     

S-band Brillouin erbium fibre laser

A multi-wavelength Brillouin erbium fibre laser, which operates in short wavelength band (S-band), is proposed and demonstrated. The system employs both linear gain and nonlinear gain from a 20 m S-band erbium-doped fibre and a 500 m singlemode fibre, respectively, to generate an optical wavelength comb with spacing of approximately 0.084 nm. Two 80/20 couplers were used in the system as an internal feedback of generated Stokes signal to produce cascaded Brillouin Stokes for multiwavelength operation. A stable output laser comb of up to seven lines was obtained with a Brillouin pump of 3.5 mW and a 980 nm pump of 200 mW.     

L频段高稳梳状谱电路设计与实现

利用阶跃恢复二极管的强非线性特点,设计了一个输入信号频率100 MHz、输出信号频率0.9～ 1.4 GHz的梳状谱电路,经开关滤波器电路处理后可以实现6个单频点输出.梳状谱电路经优化设计和调试,以较低的驱动功率实现了模块高稳定输出.在-55℃～+85℃工作温度范围内、输入信号功率0～+3 dBm条件下,梳状谱电路驱动功率为20 dBm左右,测试模块输出信号功率变化小于1.5 dB,附加相位噪声劣化小于1 dB.     

全新布里渊散射可切换微波光子滤波器

提出了一个新的基于布里渊散射效应的微波光子滤波器。该滤波器可通过调谐系统中光滤波器的中心波长,实现高解析度带通滤波器与陷波滤波器之间的灵活切换,并且通过调谐产生受激布里渊散射的泵浦光的波长可实现滤波器通带或阻带的中心频率在很大频率范围内连续调谐。该滤波器为全光结构,因此具有非常大的调谐范围（调谐上限仅受限于试验中使用的矢量网络分析仪的显示频率上限）。系统中采用相位调制器,因此没有偏置电压漂移问题。实验结果展示了一个带通与陷波滤可灵活切换的高解析度微波光子滤波器,并且通带和阻带的中心频率在9～26.5 GHz范围内连续可调谐,其中带通滤波器的通带具有极窄3 dB带宽,约28 MHz（由光纤本身布里渊增益区线宽所决定）。     

高非线性光纤中受激布里渊散射的抑制和光参量放大

受激布里渊散射 (SBS)的抑制是实现光纤参量放大的重要技术要求 ,已有文献报道多采用对抽运光进行相位调制的方法 ,将光功率分散到多个频率分量上来达到这一目的。提出一种二次调相的方法 ,在已有 2GHz相位调制的商品光源上施加 36 5MHz的二次相位调制 ,将高非线性光纤 (HNLF)的受激布里渊散射阈值由未加任何调制时的 10dBm至少提高到 2 3 5dBm ,达到了参量放大的要求。在此基础上 ,进行了连续波 (CW )抽运的光纤参量放大实验。实验中采用长度为 14 5 0m ,非线性系数γ =11 9W-1km-1,色散斜率S =0 0 15 5ps/(nm2 ·km)的高非线性光纤 ,使用外腔可调谐激光器 (ECL)作为信号光源 ,小信号增益带宽达到 2 6nm(增益 >10dB) ,峰值增益达到2 4dB。同时还观察到了由于非线性拉曼放大作用造成的长波长信号光增益大于短波长信号光增益的不对称性。     

Tunable multiwavelength Brillouin-erbium fiber laser with a polarization-maintaining fiber Sagnac loop filter

We demonstrate the generation of 12-wavelength comb with 14.5-nm tunable range in the Brillouin-Erbium fiber laser. This is achieved through tuning the gain profile of Erbium-doped fiber by a Sagnac loop filter with 18-cm polarization-maintaining fiber, in conjunction with modifying the wavelength of Brillouin pump. The experiment also demonstrates that the tunable range is closely equal to the 3-dB bandwidth of Sagnac loop filter due to its periodic transmission profile. Meanwhile, the effect of the 980-nm pump on the tunable multiwavelength generation is investigated. The power of 980-nm pump has a great effect on the wavelength number and the output power of the generated multiwavelength comb, but little on the tunable range. This technique may be applicable to multiwavelength operation lasers with a large tunable range.     

Tunable microwave photonic filter based on a fiber ring and erbium-doped fiber amplifier

The tunable microwave photonic filter based on a fiber ring and erbium-doped fiber amplifier （EDFA） was proposed. By introducing a section of erbium-doped fiber （EDF） into the fiber ring, the loss of the signal can be compensated by the EDFA gain through adjusting the pump power. This can largely increase the number of the effective sampling taps, and then improve the performance of the microwave photonic filter notably. When the pump power was set to be 42.7 roW, a microwave bandpass filter with the 3-dB bandwidth of 0.15 MHz, the Q factor up to 100 and extinction ratio up to 20 dB was achieved. By employing a tunable optical delay line in the above fiber ring, a tunable microwave photonic filter has been realized through tuning the length of the optical delay line. The proposed tunable microwave photonic filter can fred great applications in microwave signal processing and ROF system.     

基于SBS的通带可变微波光子滤波器

提出并分析了一种大范围可调谐的通带可变微波光子滤波器。它基于受激布里渊散射(SBS)效应并使用2个调制器与1个光纤布喇格光栅生成泵浦信号。通过分别调节这2个调制器的调制频率,可得双通带滤波器和通带间隔可变的四通带滤波器,并实现滤波器中心频率的大范围连续可调谐,而在整个调谐过程中,滤波器的3dB带宽保持不变。仿真分析了不同调制信号对滤波器通带及中心频率的影响,以及滤波器的带宽与泵浦的功率和SBS增益介质长度的关系。     

多波长布里渊掺铒光纤激光器的结构优化研究

基于受激布里渊散射效应(SBS)和掺铒光纤(EDF)的线性增益机理研究了一种环形腔多波长布里渊掺铒光纤激光器(BEFL)。在该激光器中使用单模光纤作为布里渊增益介质,使用掺铒光纤来放大产生的斯托克斯(Stokes)信号,使该激光器在室温下产生稳定的多波长输出。通过对激光器结构中的环行器和耦合器的位置以及耦合器的接入方式的研究与分析发现:耦合器的接入方式、环行器与耦合器的位置均对激光器的输出有影响。在可调谐光源TLS(布里渊泵浦激光器)的功率大小为14dBm,980nm泵浦激光器的功率大小为23dBm,单模光纤长度为10km的情况下进行了实验测试,结果表明:耦合器的接入方式对BEFL的输出影响很明显,最后给出了详细的测试结果和相应解释。     

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.     

波长间隔为20 GHz的多波长布里渊光纤激光器

设计了一种基于环形腔的双倍布里渊频移间隔的可调谐光纤激光器实验装置。 该实验装置由一个3 dB耦合器、一台可调谐激光源(TLS)、一台980 nm泵浦和一个实现双倍布里渊频移环形腔构成。该结构耦合输出偶数阶Stokes光,从而实现间隔约为20 GHz或0.16 nm的多波长输出。并研究了980 nm泵浦光和BP光功率对输出偶数阶Stokes光波数的影响。当980 nm 泵浦功率固定为26 dBm(400 mW),BP功率为10 dBm时,获得了间隔为0.16 nm的11个稳定激光输出以及36 nm(1530~1566 nm)的可调谐范围。     

Vertical-cavity amplifying modulator at 1.3 μm

The modulation/switching properties of a vertical-cavity semiconductor optical amplifier operating at 1.3 μm wavelength are investigated. The device was optically pumped and operated in reflection mode. A 150-mV (100 mA) modulation of the drive to the pump source produced a 7-dB modulation of the pump power, which produced a 35-dB modulation in the output signal. The maximum extinction ratio was 35 dB, and limited by device heating. Frequency response measurements revealed a modulation bandwidth of 1.8 GHz when the amplifier was saturated. This enabled 2.5-Gb/s modulation of a -10 dBm input signal with 5.5-dB fiber-to-fiber gain     

Characteristics of a semiconductor laser pumped brillouin amplifier with electronically controlled bandwidth

We demonstrate the operation of a semiconductor laser pumped fiber Brillouin amplifier. An optical gain of 5.5 dB/mW of pump power is obtained. The 15-MHz intrinsic bandwidth of the amplifier was extended more than one order of magnitude by adding frequency modulation to the pump laser. Bit-error-rate receiver sensitivity measurements with an in-line Brillouin amplifier demonstrate a 16-dB improvement in the system gain at 10 Mbit/s and a 8.5-dB improvement at 90 Mbit/s. Noise calculations show that the amplifier has an excess noise factor of 50-500 depending on the amplifier length and pump power.     

正弦型相柑位调制对闲频光展宽抑制的研究

理论分析了双抽运光纤光参量放大POPA系统中抽运光相位调制对闲频光光谱展宽的影响,提出可以采用多个耦合的低频正弦信号对两路抽运光进行反相相位调制,在提高受激布里渊散射(SBS)阈值的同时抑制闲频光光谱的展宽。通过采用300MHz与900MHz的耦合信号作为调制信号,实验演示了该方案的可行性,得到无展宽的闲频光。比较了传统PRBS信号作为调制信号的方案,发现采用正弦调制信号对系统器件的性能有更好的容忍度。     

An image-rejecting mixer and vector filter with 55-dB imagerejection over process, temperature, and transistor mismatch

This paper describes an image-rejecting mixer and vector filter for use in radio systems with channel bandwidths in the range of 1 MHz. The circuit replaces the SAW filter and second downconverter commonly used in this style of radio. Because the output of the circuit is at an IF of 5 MHz, traditional demodulation methods including limiting and FM discrimination can still be used. The circuit is based on a quadrature mixer that guarantees good performance despite device mismatches and process variation. The circuit consumes 29 mA at 3.3 V,and achieves better than 55-dB image rejection despite device mismatches and process variation and is implemented in a single-poly triple metal 0.5 μm CMOS process with linear capacitor implants. The circuit is designed for input signals from 125 to 250 MHz. Input referred voltage noise is 900 μVrms. The in-band IP3 is 18 dBm. By changing an external reference frequency, the passband width of the filter can be varied from 3 to 0.5 MHz     

A low-power low-noise accurate linear-in-dB variable-gain amplifierwith 500-MHz bandwidth

A linear-in-dB variable-gain amplifier (VGA) using a pre-distortion circuit to generate the gain-control signal is fabricated in a BiCMOS process with f_T=20 GHz. The VGA comprises two cascaded stages of signal-summing VGA and has a variable-gain range of over 70 dB. It can operate at up to 500 MHz and dissipates 36 mW from a 3-V supply. A noise figure of below 5 dB and IIP3 of over -38 dBm at 43-dB gain were obtained. The VGA achieved a gain error of less than 2 dB over 70-dB gain range, and it occupies approximately 1 mm². The VGA is applicable to future code division multiple access (CDMA) receivers     

增益钳制掺铒光纤放大器特性研究

报道了一种新型基于环形激光腔的增益钳制掺铒光纤放大器。得到了较好的增益钳制效果和增益平坦度,利用980nm半导体激光器泵浦12m长掺铒光纤形成激光增益,观测到 30nm增益带宽。通过反馈1520nm 激光,在可变衰减器不同值测量了输入信号从- 40 ～10dBm的增益,其小信号增益被钳制在16dB。可为40个波分复用(WDM)信道波长提供增益钳制及平坦的放大功能。     

复合滤波结构的窄线宽高频微波信号产生装置

为了在较低泵浦功率下实现单纵模双波长激光信号的输出,进而获得窄线宽的高频微波信号,设计并实验了一种基于复合滤波结构的窄线宽高频微波信号产生装置。通过8字腔结构布里渊增益腔和反射式光纤光栅构成的波长选择滤波器实现了4倍布里渊频移间隔的双波长斯托克斯光信号输出,采用200 m长单模光纤作为增益介质,同时与50 m长单模光纤构成级联光纤环结构,采用三端口耦合器与2 m长未泵浦的保偏掺铒光纤构成萨格纳克环结构,利用级联光纤环结构和萨格纳克环结构的复合滤波作用实现了斯托克斯光信号模式的选择,使输出的斯托克斯光信号由多纵模运行状态变为单纵模运行状态。实验证明:通过对输出的单纵模双波长斯托克斯光信号进行拍频检测可得42.85 GHz的高频微波信号产生,线宽为38 kHz;通过改变可调谐泵浦激光器的输出波长,可实现42.25~43.51 GHz范围内的频率调谐;通过稳定性测试,产生的42.85 GHz高频微波信号的频率变化在0.83 MHz内,峰值功率变化在±0.8 dB内,稳定性良好,满足实际应用需求。