160 Gbit/s wavelength shifting and phase conjugation usingperiodically poled LiNbO3 waveguide parametric converter

High efficiency 160 Gbit/s wavelength conversion and optical phase conjugation using cascaded nonlinearities in periodically poled LiNbO ₃ waveguides is reported. The authors also report on use of this device as a dispersion compensator for transmission of 100 Gbit/s OTDM data through 160 km of singlemode fibre     

Optical amplification at 0.54 /spl mu/m by Tb/sup 3+/-doped fluoride fibre

0.54 mum band amplification using Tb³⁺-doped fluoride fibre is demonstrated. Spectroscopic properties of Tb³⁺-doped fluoride glass are clarified. A gain of 5.3 dB has been obtained in a 1 wt.% Tb³⁺-doped fluoride fibre for a signal power of -30 dBm by forward pumping at a wavelength of 0.488 mum with power of 100 mW     

Broadband diode-pumped fibre laser

Reports the observation of a strong dependence of the emission spectrum (centre wavelength and linewidth) of Nd:silica fibre lasers on pump wavelength. In a particular fibre, careful selection of the pump wavelength has led to the operation of a broadband fibre laser at 1060 nm with 19 nm FWHM bandwidth. When pumped with a 30 mW diode laser, it exhibits a 1 mW threshold, a 2.5 mW output, and an intrinsic average wavelength temperature stability of about 10 p.p.m./°C     

Gain flattened Er3+-doped tellurite fibre amplifier forWDM signals in the 1581-1616 nm wavelength region

A gain-flattened Er³⁺-doped tellurite fibre amplifier (EDTFA) with an expanded L-band is presented. The amplifier has an average gain of 28 dB and a noise figure of <6 dB with a slight gain excursion of 1 dB over a wide wavelength range of 1581-1616 nm. The total output power of the EDTFA module was 20.5 dBm and its power conversion efficiency reached 25%     

All-optical wavelength conversion with large wavelength hopping by utilizing multistage cascaded SOA-based wavelength converters

A novel broadband wavelength converter by multistage cascaded semiconductor optical amplifier (SOA)-based wavelength converters is proposed. We have demonstrated, for the first time, broadband wavelength conversion in the wavelength range of 1320-1610 nm by using three-stage cascaded SOA-based wavelength converters with each different gain band.     

Bismuth oxide nonlinear fibre-based 80 Gbit/s wavelength conversion and demultiplexing using cross-phase modulation and filtering scheme

Reported is the experimental demonstration of wavelength conversion and subsequent demultiplexing of an 80 Gbit/s OTDM signal using the cross-phase modulation and spectral filtering technique in short lengths of bismuth oxide-based nonlinear fibre with a nonlinearity of /spl gamma/=/spl sim/1100 W/sup -1/ /spl middot/ km/sup -1/. Error-free, overall operation is readily achieved over a wavelength tuning range of /spl sim/10 nm.     

Narrow line semiconductor laser using fibre grating

A narrow linewidth, low chirp, wavelength selectable, packaged alternative to current DFB structures has been developed which employs a fibre reflection grating incorporated in the fibre pigtail. The wavelength of the packaged device can be determined by the appropriate choice of fibre grating coupled to the antireflection coated facet of a 1.55 mu m BH laser. Linewidths of less than 50 kHz, sidemode suppression of more than 30 dB and chirp when modulated at 1.2 Gbit/s of <0.5 MHz have been demonstrated.<>     

一种可调谐的宽带喇曼波长转换器

为了提高宽带波长转换技术的响应速度，采用高非线性光子晶体光纤，设计了一种受激喇曼散射的可调谐全光宽带波长转换器。基于光纤中喇曼效应，对光子晶体光纤喇曼增益谱采取高斯曲线进行拟合，建立了喇曼波长转换器的理论模型，并进行了仿真分析，讨论了光纤长度对转换效率的影响。结果表明，在符合通信系统的条件下，实现了100nm转换带宽，波段为1487nm~1587nm，Q因子随探测光波长变化与喇曼增益谱走势相同，其波长转换质量最优处在喇曼增益系数最大处。该研究对未来光网络的波长转换器波长分配以及光纤长度的配置研究具有参考意义。     

Two-mode fibre spatial-mode converter using periodic coredeformation

Efficient conversion between the LP₀₁ and LP₁₁ modes in a two-mode fibre is achieved by periodically ablating the fibre surface with a CO₂ laser and then annealing the fibre with an electric arc. The resulting periodic core deformation produces 99% mode conversion over a 37 nm bandwidth around 1540 nm and 0.38 dB insertion loss     

Strong photoinduced Bragg gratings in arsenic selenide optical fibre using transverse holographic method

Fabrication of strong fibre Bragg gratings in singlemode arsenic selenide (As₂Se₃) fibre for use at telecom wavelengths by the transverse holographic method is reported. Photoinduced decrease in the material refractive index was achieved using low-intensity CW illumination at a wavelength of 785 nm. A peak grating strength of 23.7 dB is seen, with inferred change in the average refractive index as large as 4.7 times 10^-3.     

Broadband photorefractive properties and self-pumped phase conjugation in Ce-SBN:60

The first use of cerium-doped Sr0.6Ba0.4Nb2O6as a broadband self-pumped phase-conjugate mirror using internal reflection is reported. The phase-conjugate reflectivity at normal incidence ranged from two percent at 442 nm to seven percent at 515 nm and was zero at 633 nm. The electron-hole competition was found to be significant and had a wavelength dependence in one sample but not the other. The charge carrier density wassim 7 times 10^{16}cm^-3and was wavelength in-dependent. The absorption coefficient ranged from 2 cm^-1at the shorter the wavelengths to zero at longer wavelengths. The dispersion in the indexes of refraction was measured and the birefringence was -0.036. The sign of the dominant charge carriers was determined to be negative and the sign of the electrooptic coefficient, r33, was positive. Using the above values, a wavelength dependent coupling coefficient has been determined. The experimental results indicate that the phaseconjugate reflectivity decreases at shorter wavelengths due to increased absorptive losses and experiences a threshold effect at longer wavelengths.     

High-Speed (60 GHz) and Low-Voltage-Driving Electroabsorption Modulator Using Two-Consecutive-Steps Selective-Undercut-Wet-Etching Waveguide

Based on a novel structure of waveguide, a broadband electroabsorption modulator (EAM) with low driving voltage and high extinction ratio has been demonstrated in this letter. The waveguide of InGaAsP-InP p-i-n layer structure is fabricated by two consecutive steps of selective undercut-wet-etching: 1)HCl : H₃PO₄ on p-InP (p- layer), and 2)H₃PO₄ : H₂O₂ : H₂O on InGaAsP (active region), showing a wide ridge with a narrow undercut active region. Low capacitance and low cladding impedance can thus be simultaneously attained in such waveguides, leading to low microwave loss and high-speed electrooptical (EO) response. A ridge as wide as 8 mum with a 3-mum- wide active region and a 450-nm gap height in the undercut portion has been fabricated. A 350- mum -long waveguide of EAM is designed, revealing a high extinction ratio of > 30 dB (D.C.) and a modulation efficiency of > 20 dB/V (D.C.) with polarization-insensitive operation at a wavelength of 1550 nm. As high as 60 GHz of a 3-dB bandwidth is measured in the high-speed EO conversion. Calculations by an equivalent circuit model are quite fitted with the measurement, revealing that broadband performance is mainly attributed to the low microwave propagation loss in such waveguides.     

Efficient second harmonic conversion of broad-band high-peak-powerNd:glass laser radiation using large-aperture KDP crystals in quadrature

The authors have investigated the second-harmonic conversion efficiency of broadband Nd:glass laser light (Δν/c<30 cm^-1 FWHM). Using two KDP crystals in a quadrature arrangement, they obtain energy conversion efficiencies of ≈55% with an initial bandwidth for the fundamental of Δν/c≈17 cm^-1 FWHM. For these conditions, a modest increase (≈70%) was observed in the harmonic bandwidth (FWHM) relative to the fundamental. The usual theory of three-wave mixing in dispersive birefringent nonlinear crystals is extended to describe the broadband harmonic conversion process; the generalized theory includes the statistical properties of the light and phase mismatch effects on the spectral components in the complex field amplitudes. Good agreement is found between the code calculations and the measurements     

Excimer laser writing of submicrometre period fibre Bragg gratingsusing phase-shifting mask projection

Submicrometre period, first-order Bragg gratings have been written in optical fibre, for the first time to the authors knowledge, by projecting a phase-shifting mask. Gratings with a peak reflectivity of 85% at a Bragg wavelength of 1530 nm were recorded using single pulses from a broadband KrF excimer laser     

Multimode fibre baseband frequency response measurement with single frequency output extracted from modulated InGaAsP laser

A new method to measure multimode fibre frequency response is presented by using a single longitudinal mode extracted from modulated semiconductor laser output. Intensity fluctuation noise, caused by r.f. modulation, is utilised as a broadband baseband signal. Baseband frequency response of a 1.98 km graded-index fibre is measured up to 1.5 GHz in 1.1?1.5 ?m wavelength region. This method provides a simple and accurate measurement of intermodal dispersion excluding chromatic dispersion effect.     

Optically transparent digitally tunable wavelength filter

A new digital architecture combining a spatial light modulator written dynamic hologram and a fixed diffractive grating has been demonstrated to produce a tunable wavelength filter with a tuning resolution of 2.5 nm over a 160 nm range. Three modes of a broadband 1.45 μm laser diode have been isolated using the filter and selectively coupled into singlemode communications fibre     

An Ultra-Wideband High-Linearity CMOS Mixer With New Wideband Active Baluns

A 2-11-GHz high linearity CMOS down-conversion mixer with wideband active baluns using 0.18-mum CMOS technology is demonstrated in this paper. The mixer employs a folded cascode Gilbert cell topology and on-chip broadband active baluns. The folded cascode approach is adopted to increase the output swing, and the linearity is enhanced by a harmonic distortion canceling technique derived from the harmonic balance analysis. The proposed configuration shows the highest IIP₃ and IP_{1 dB}, and exhibits more compact size than most published studies. A broadband active balun is used to generate wideband differential signals, together with the derivation of a closed-form expression for the phase imbalance. This single-ended wideband mixer has the conversion gain of 6.9plusmn1.5 dB, input 1-dB compression point (IP_{1 dB}) of - 3.5 dBm, single-sideband noise figure of 15.5 dB, and third-order input intercept point (IIP₃) of 6.5 dBm under the power consumption of 25.7 mW from a 1.8-V power supply. The chip area is 0.85 x 0.57 mm².     

Chirp reduction in wavelength conversion using a laser diode byinjection locking

The authors demonstrate that an injection locking technique suppresses the chirp in wavelength conversion using a laser diode. Waveform patterns of a 2.5 Gbit/s intensity-modulated signal after 128 km transmission through a normal dispersion singlemode fibre were improved by the injection locking technique     

A 25–75 GHz Broadband Gilbert-Cell Mixer Using 90-nm CMOS Technology

A compact and broadband 25-75-GHz fully integrated double-balance Gilbert-cell mixer using 90-nm standard mixed-signal/radio frequency (RF) CMOS technology is presented in this letter. A broadband matching network, LC ladder, for Gilbert-cell mixer transconductance stage design is introduced to achieve the flatness of conversion gain and good RF port impedance match over broad bandwidth. This Gilbert-cell mixer exhibits 3plusmn2dB measured conversion gain (to 50-Omega load) from 25 to 75GHz with a compact chip size of 0.30mm². The OP_{1 dB} of the mixer is 1dBm and -4dBm at 40 and 60GHz, respectively. To the best of our knowledge, this monolithic microwave integrated circuit is the highest frequency CMOS Gilbert-cell mixer to date     

High-power cascaded Raman fibre laser using phosphosilicate fibre

A 13.2 W second cascade phosphosilicate cascaded Raman fibre using a 450 m phosphosilicate singlemode optical fibre is demonstrated. The lasing wavelength is 1539 nm and the conversion efficiency is 32.5%. This is the highest output power ever reported from a cascaded Raman fibre laser in the 1400-1600 nm range.