Gain and output-saturation limit evaluation in Pr/sup 3+/-doped fluoride fiber amplifier operating in the 1.3 mu m band

The optical amplification characteristics in a Pr/sup 3+/-doped fluoride fiber have been demonstrated. The amplification band in a Pr/sup 3+/-doped fluoride fiber fully covers the 1.3 mu m telecommunication window, and a practical optical gain value of over 13 dB was obtained. Moreover, a saturation power of +9 dBm was attained. If the problems of pumping efficiency and wavelength are solved, Pr/sup 3+/-doped fluoride fiber will become available for 1.3 mu m booster amplifiers.<>     

Performance of a reconfigurable wavelength converter based ondual-pump-wave mixing in a semiconductor optical amplifier

We report on a wavelength converter based on dual pump wave mixing in an 1-mm-long bulk semiconductor optical amplifier. Very high conversion efficiency (more than 0 dB) and signal-to-background-noise ratio (SBR) (16 dB), for large down- or up-wavelength shifts (30 mn) has been achieved using parallel polarized pumps with low optical power (-13 dBm). Orthogonal polarized pumps result in worse performance, having the advantage of polarization insensitivity for small wavelength spacing between them. The converter operates in a fixed input-tunable output or a tunable input-fixed output mode of operation. In each mode, the measured SBR is almost independent of the wavelength shift for either up- or down-conversion     

Optical data inversion by locking mode competition

Using the behaviour of a Fabry-Perot semiconductor laser under the injection of two optical beams, all-optical data inversion is demonstrated without changes in the data carrier wavelength, together with a simultaneous wavelength conversion without data inversion. The output optical power at the inverted binary one state (-12 dBm) is greater than that corresponding to the inversion threshold (-16 dBm), which enables such operations to be repeated several times in cascade. These operations have been performed at a bit rate of 2 Gbit/s at 1.55 /spl mu/m.     

40 Gbit/s all-optical clock recovery using two-section gain-coupledDFB laser and semiconductor optical amplifier

40 Gbit/s wavelength and polarisation insensitive all-optical clock recovery using a two-section distributed feedback (DFB) laser has been demonstrated. The polarisation sensitivity of the two-section DFB laser was solved by converting incoming data onto a local laser through cross-gain modulation using a semiconductor optical amplifier. The scheme has a sensitivity of -13 dBm     

Monolithic PIN-HEMT receiver with internal equaliser for long-wavelength fibre optic communications

An optical receiver, in which a GaInAs PIN photodiode, an AlInAs/GaInAs HEMT high impedance amplifier and even an equaliser were integrated monolithically on an InP substrate, has been fabricated. An optical sensitivity of -30.4 dBm was obtained at 1.2 Gbit/s and 1.3 mu m wavelength.<>     

Optical self-homodyne DPSK transmission at 1 and 2 Gbit/s over 86 km of fibre

Optical self-homodyne DPSK transmission has been achieved at 1 and 2 Gbit/s data rates with respective receiver sensitivities of ?34.4 dBm and ?32.4 dBm at 10?9 BER. No dispersion penalty was observed after transmission through 86 km of optical fibre with 17 ps/?m/km dispersion at the operating wavelength of 1.53 ?m.     

A design and experimental results of the OS-280M optical submarine repeater circuits

This paper describes the design philosophy and the experimental results of the optical submarine repeater for the OS-280M optical fiber submarine cable system to be installed across the ocean. This repeater which employs the information rate of 280 Mbit/s, the optical wavelength of 1.3 μ, and is implemented with monolithic ICs, features high reliability, long repeater spans, and the supervisory systems. The test results show that the average optical output power is - 1.4 dBm for the mark density of 1/2, the minimum average power of the optical input for the BER 10 is about -38 dBm at the room temperature, and other specifications are also well satisfied.     

30 dB optical net gain at 1.543 mu m in Er/sup 3+/ doped fluoride fibre pumped around 1.48 mu m

A 30 dB optical net gain and 12 dBm maximum output power for -1 dBm signal input have been measured at a signal wavelength of 1.54 mu m with an erbium doped ZBLAN fibre pumped at 1.47-1.48 mu m. The results confirm the great potential of ZBLAN fibres for hosting rare earth ions to generate optical amplification. The discussion points out the parameters to be studied to improve the fibre amplifier performance.<>     

Erbium-doped optical fiber amplifiers pumped in the 660- and 820-nmbands

State-of-the-art erbium (Er)-doped optical fiber amplifiers (EDFA's) pumped in the 660- and 820-nm bands are described. We have demonstrated highly efficient EDFA's incorporating optimized 664- and 827-nm pump wavelengths and an Er-doped high numerical aperture (NA) fiber with thermally diffused expanded core (TEC) fiber ends. Gain coefficients of 3.8 and 1.3 dB/mW at respective wavelengths of 664 and 827 nm were achieved at a signal wavelength of 1535 nm. Noise figures of 3.1 and 4.1 dB at respective pump wavelengths of 670 and 827 nm were obtained at a signal wavelength of 1535 nm. A highly efficient Er-doped fiber amplifier module, in which an AlGaInP visible laser diode (LD) was used as the pump source, was successfully developed as a practical application of this technology. A maximum overall gain coefficient of 3.0 dB/mW was achieved at a signal wavelength of 1535 nm. The EDFA module realized a maximum overall signal gain of 33 dB at 1535 nm with a saturated output power of -1 dBm. A maximum saturated output power of 3.9 dBm was obtained at a signal wavelength of 1552 nm. The present EDFA design using a low-cost laser diode for optical disk memory use and a high NA Er-doped fiber has great potential for providing inexpensive, high-performance EDFA's     

High-output-power polarization-insensitive semiconductor optical amplifier

A high-output-power 1550 nm polarization-insensitive semiconductor optical amplifier (SOA) was developed for use as a compact in-line optical amplifier. A very thin tensile-strained bulk structure was used for the active layer and active width-tapered spot-size converters (SSCs) were integrated on both input and output sides. The SOA module exhibited a high saturation output power of +17 dBm together with a low noise figure of 7 dB, large gain of 19 dB, and low polarization sensitivity of 0.2 dB for optical signals of 1550 nm wavelength. For the amplification of optical signals modulated at 10 Gb/s in the nonreturn-to-zero (NRZ) format, a good eye pattern without waveform distortion due to the pattern effect was obtained at an average output power of up to +12 dBm. Additionally, good amplification characteristics were demonstrated for the signal wavelength range corresponding to the C-band.     

Chromatic Dispersion Compensation via Mid‐span Spectral Inversion with Periodically Poled LiNbO3 Wavelength Converter at Low Pump Power

Mid‐span spectral inversion (MSSI) has to utilize high optical pump power, for its operation principle is based on a nonlinear optical wavelength conversion. In this paper, a low pump‐power operation of MSSI‐based chromatic dispersion compensation (CDC) has been achieved successfully, for the first time to our knowledge, by introducing a noise pre‐reduction scheme in cascaded wavelength conversions with periodically poled LiNbO₃ waveguides at a relatively low operation temperature. As preliminary studies, phase‐matching properties and operation‐temperature dependence of the wavelength converter (WC) were characterized. The WC pumped at 1549 nm exhibited a wide conversion bandwidth of 59 nm covering the entire C‐band and a conversion efficiency of –23.6 dB at 11 dBm pump power. CDC experiments were implemented with 2.5 and 10 Gb/s transmission systems over 100 km single‐mode fiber. Although it is well‐known that the signal distortion due to chromatic dispersion is not critical at a 2.5 Gb/s transmission, the clear recovery of eye patterns was identified. At 10 Gb/s transmission experiments, eye patterns were retrieved distinctly from seriously distorted ones, and notable improvements in bit‐error rates were acquired at a low pump power of 14 dBm.     

622-Mb/s Bidirectional SFP Optical Transceiver Using an Integrated WDM Optical Subassembly

The 1.3/1.55-mum bidirectional small form pluggable (SFP) optical transceiver with an integrated wavelength division multiplexing (WDM) subassembly using accurate ceramic blocks has been developed. The WDM subassembly on which a laser diode, a receiver photodiode, a WDM filter, and two microlenses are integrated is only 2.0 times 2.1 times 0.6 mm³ in size and inserted in a TO-CAN package. The SFP transceiver coupled with single-mode fiber has been operated at a 622-Mb/s data rate. The transmitted optical output power is -2.8 dBm and the measured value of sensitivity is -32 dBm at 10^-10 bit-error rate.     

ROF系统中基于SOA非线性效应的光子上变频技术研究

在光载射频（ROF）系统中,为了将承载信息的光基带信号上变频到微波／毫米波波段,本文基于半导体光放大器（SOA）中的交叉增益调制（xGM）和交叉相位调制（XPM）效应实现了光子上变频：即实现了1．25Gb／s基带信号到30GHz的毫米波信号的转换。文中分析了SOA驱动电流的变化（50～200mA）和信号光与本振光波长间...     

High-performance compact optical WDM transceiver module for passivedouble star subscriber systems

High-performance transceiver-type optical WDM interface modules with a volume of only 36 cc have been developed for PDS subscriber systems. The new module comprises an optical WDM sub-module, hybrid-integrated transmitter and receiver circuits. In the WDM sub-module, a planar lightwave circuit chip was hermetically sealed together with laser and photodiode chips in order to minimize the size of the transceiver module. The lightwave circuit was formed on an optical-waveguide chip by adopting a high-silica based optical-waveguide technology. The circuit has a 3-dB directional coupler for bi-directional transmission with a 1.3-μm wavelength through a single fiber and a wavelength division multiplexer between both 1.3-μm and 1.55-μm wavelengths. The overall characteristics of the fabricated WDM sub-module achieved were a responsitivity of 0.25±0.05 A/W, an insertion loss approximately 3 dB at 1.55 μm and an isolation of 35 dB between both wavelengths. Optical output power of the fabricated transceiver module was -3.8 dBm. Also, receiver sensitivity of less than -35 dBm with an overload of over -14 dBm were obtained by introducing high-speed automatic gain and threshold control techniques. Thus, an allowable span loss of over 30 dB and an optical dynamic range of over 20 dB were attained. The preamble bit length required to reach stable receiver operation was confirmed to be within three bits     

The first hot pluggable 2.5 Gb/s DWDM transceiver in an SFP form factor

For the first time, a hot pluggable 2.5 Gb/s DWDM transceiver with 100 GHz spacing in an SFP form factor has been presented. We demonstrate transmit wavelength drift of plusmn9 pm and optical output power stability of 0.2 dB over an operating case temperature range of -5degC to 70 degC. The minimum receive sensitivity was -33.2 dBm for back-to-back, -32.6 dBm after transmission over 80 km of standard SMF, and -28 dBm for an OSNR level of 16 dB at a BER of 1 times 10^-10      

High-performance avalanche photodiode with separate absorption `grading? and multiplication regions

High-speed operation of avalanche photodiodes with separated absorption and multiplication regions has been achieved by incorporating an intermediate bandgap InGaAsP `grading? layer between the InP multiplication layer and the InGaAs absorption layer. These APDs also exhibit low dark currents, high quantum efficiencies and good avalanche gains. Sensitivity measurements have been made at 1.3 ?m and 1.55 ?m with one of these APDs in a high-speed optical receiver: at bit rates of 420 Mbit/s and 1 Gbit/s the minimum average powers required for 10?9 BER are ?43 dBm and ?38 dBm at 1.55 ?m, and ?41.5 dBm and ?37.5 dBm at 1.3 ?m, respectively.     

27-dB gain unidirectional 1300-nm polarization-insensitive multiplequantum well laser amplifier module

An unidirectional polarization-insensitive multiple quantum well laser amplifier module for the 1300-nm window with a record high gain of 27 dB and a 3-dB saturation output power of 13 dBm is demonstrated. The module gain has a 3-dB width exceeding 60 nm and shows a typical polarization sensitivity and gain ripple as low as 0.3 dB. To provide immunity for backscattered or reflected light, polarization independent optical isolators were inserted in the input and output coupling optics of the package. A practical optical amplifier module for the 1300-nm window is very desirable, because most of the presently installed fiber has its zero dispersion wavelength around 1310 mm, while much of the older fiber often only can be operated around this wavelength     

Bidirectional hybrid OFDM based Wireless-over-fiber transport system using reflective semiconductor amplifier and polarization multiplexing technique

In this paper, a bidirectional hybrid OFDM based Wireless-over-fiber architecture has been investigated and demonstrated to transmit 10 Gbps as well as 6.25 Gbps OFDM data for downlink transmission and 5 Gbps as well as 2.5 Gbps OFDM data for uplink transmission over 50-km single mode fiber (SMF) employing polarization multiplexing technique (POLMUX) at optical line terminal (OLT) and optical network unit (ONU). The POLMUX technique is exercised by polarization beam splitters and polarization beam combiners. Mach-Zehnder modulator and RSOA have been used for modulation at OLT and ONU respectively. Transmission performances are observed by constellation diagrams, EVM and BER values. For 10 Gbps, 6.25 Gbps down-link signal and 5 Gbps, 2.5 Gbps up-link signal the power penalty of 3 dBm, 2.3 dBm and 4 dBm, 3.2 dBm at a BER of 10⁻⁹ between back-to-back and over 50-km SMF plus 10-m and 5-m wireless link, are observed respectively. For 32-QAM < 10.5% EVM and for 16-QAM < 13% EVM are recorded. Our architecture is a prominent alternative, not only due to its have potential of both optical and wireless technology but also it is offers a powerful platform to communicate high data rates and support various type of future unforeseen applications and services.     

Quantum-Dot Semiconductor Optical Amplifiers

This paper reviews the recent progress of quantum-dot semiconductor optical amplifiers developed as ultrawideband polarization-insensitive high-power amplifiers, high-speed signal regenerators, and wideband wavelength converters. A semiconductor optical amplifier having a gain of > 25 dB, noise figure of < 5 dB, and 3-dB saturation output power of > 20 dBm, over the record widest bandwidth of 90 nm among all kinds of optical amplifiers, and also having a penalty-free output power of 23 dBm, the record highest among all the semiconductor optical amplifiers, was realized by using quantum dots. By utilizing isotropically shaped quantum dots, the TM gain, which is absent in the standard Stranski-Krastanow QDs, has been drastically enhanced, and nearly polarization-insensitive SOAs have been realized for the first time. With an ultrafast gain response unique to quantum dots, an optical regenerator having receiver-sensitivity improving capability of 4 dB at a BER of 10^-9 and operating speed of > 40 Gb/s has been successfully realized with an SOA chip. This performance achieved together with simplicity of structure suggests a potential for low-cost realization of regenerative transmission systems.     

High-speed monolithic silicon photoreceivers on high resistivityand SOI substrates

We compare monolithic silicon optical receivers fabricated on high resistivity and silicon-on-insulator (SOI) substrates. Each receiver consisted of a lateral p-i-n photodiode and an NMOS transimpedance preamplifier. At a drain voltage (V_DD) of 3.5 V, a photodiode voltage (V_PD) of 30 V, and a wavelength of 850 nm, the high resistivity receiver exhibited sensitivities of -31.9 dBm at 622 Mb/s and -23.2 dBm at the maximum operating speed of 1.0 Gb/s. At V_DD =5 V and V_PD=20 V, the sensitivity of the SOI receiver was -26.1 dBm at 622 Mb/s, -20.2 dBm at 1.0 Gb/s and -12.2 dBm at the maximum speed of 2.0 Gb/s. Single supply operation at 5 V and 3 V was also demonstrated for the SOI receiver. Methods for extending the speed and improving the sensitivity characteristics in more advanced technologies with lower supply voltages are discussed