Highly efficient Er-doped fibre amplifiers pumped in 660 nm band

High gain coefficient in an erbium-doped fibre amplifier, 3.8 dB/mW at 1.536 mu m and 2.3 dB/mW at 1.552 mu m, is achieved for a pump wavelength of 664 nm by using an erbium-doped fibre with a high numerical aperture of 0.285 and thermally-diffused expanded core fibre ends. The gain at 1.536 mu m reaches 30 and 35 dB for launched pump powers of 10 and 15 mW, respectively.<>     

Electron-beam vapour-deposited erbium-doped glass waveguide laser at 1.53 mu m

A single-transverse-mode erbium-doped glass waveguide laser operating at a wavelength of g 1.53 mu m is described. The erbium-doped GeO/sub 2/-SiO/sub 2/ core of the waveguide was made by electron-beam vapour deposition and patterned by reactive ion etching on a quartz glass substrate. The core was 10 mu m wide, 8 mu m high and 64.5 mm long, which permitted single-transverse-mode laser oscillation. The threshold pump power for CW oscillation was 150 approximately 200 mW at a pumping wavelength of 0.98 mu m.<>     

Mutual signal gain saturation in Er/sup 3+/-doped fibre amplifier around 1.54 mu m wavelength

Signal gain saturation characteristics of a 1.48 mu m wavelength laser diode pumped Er/sup 3+/-doped fibre amplifier are experimentally investigated for two signal channels amplified around the gain peak wavelengths of 1.535 mu m and 1.551 mu m. The degree of gain saturation is uniquely determined by the total output power when the signal wavelengths are closely positioned. This feature is not suited to two-channel amplification for widely spaced wavelengths.<>     

Laser emission and amplification at 1.3 mu m in neodymium-doped fluorophosphate fibres

Laser emission and amplification have been studied in the 1.3 mu m spectral region on the /sup 4/F/sub 3/2/-/sup 4/I/sub 13/2/ transition in Nd/sup 3+/-doped fluorophosphate singlemode fibres. Pumping at 800 nm yields an extracted laser power of 10 mW at 1.323 mu m. A gain higher than 3 dB was obtained at the same wavelength in the amplifier experiment.<>     

Ge/SiO/sub 2/ laminated optical polarizer for the wavelength region 0.6-1 mu m

A report is presented on laminated polarizers (LAMIPOLs) suitable for short wavelengths of light ( lambda <1 mu m). This new device consists of periodic alternative layers of ultrathin Ge (e.g., <8 nm thick) and SiO/sub 2/ (e.g., <1 mu m thick). The quality factor of the new laminated polarizer, defined by R= alpha /sub TE// alpha /sub TM/, is in excess of 200 at lambda =0.8 mu m and is a decreasing function of the wavelength lambda . This is in remarkable contrast to the fact that the quality factor for an Al/SiO/sub 2/ LAMIPOL is an increasing function of lambda .<>     

Highly efficient integrated optical fibre amplifier module pumped by a 0.98 mu m laser diode

A small fibre amplifier module pumped by a 0.98 mu m LD has been fabricated. Using a low erbium content fibre with a 4.9 dB/mW gain coefficient, the module attained 33 dB gain at 1.535 mu m with only 80 mA drive current.<>     

Second harmonic generation in GeO/sub 2/ ridge waveguide

Reports the first observation of 'seeded' second harmonic generation in a GeO/sub 2/ and P/sub 2/O/sub 5/ codoped silica ridge waveguide from a pump wavelength at 1.064 mu m. A 200-fold increase over the background signal has been measured.<>     

Long-wavelength In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As large-area avalanche photodiodes and arrays

Large-area (500-/spl mu/m diameter) mesa-structure In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APDs) are reported. The dark current density was /spl sim/2.5/spl times/10/sup -2/ nA//spl mu/m/sup 2/ at 90% of breakdown; low surface leakage current density (/spl sim/4.2 pA//spl mu/m) was achieved with wet chemical etching and SiO/sub 2/ passivation. An 18 /spl times/ 18 APD array with uniform distributions of breakdown voltage, dark current, and multiplication gain has also been demonstrated. The APDs in the array achieved 3-dB bandwidth of /spl sim/8 GHz at low gain and a gain-bandwidth product of /spl sim/120 GHz.     

Vertical-cavity amplifying photonic switch at 1.5 /spl mu/m

The development of a fast amplifying switch operating at 1.55-/spl mu/m wavelength is of particular interest as the active element in optical communication systems. We report the first vertical-cavity amplifying photonic switch (VCAPS) at 1.55-/spl mu/m wavelength, with a 14-dB gain and 10-ps commutation time. This structure is fabricated by the epitaxial lift-off technique and is composed of a resonant periodic gain multiple quantum wells active layers sandwiched between a SiO/sub 2/-Au back mirror based on a Si substrate and a Si-SiO/sub 2/ front mirror.     

Germania-based core optical fibers

Germania-glass-based core silica glass cladding single-mode fibers (/spl Delta/n up to 0.143) with a minimum loss of 20 dB/km at 1.9 /spl mu/m were fabricated by the modified chemical vapor deposition (MCVD) method. The fibers exhibit strong photorefractivity with the type-IIa-induced refractive-index modulation of 2/spl times/10/sup -3/. The Raman gain of 300 to 59 dB/(km/spl middot/W) was determined at 1.07 to 1.6 /spl mu/m, respectively, in a 75 mol.% GeO/sub 2/ core fiber. Only 3 m of such fibers are enough for the creation of a 10-W Raman laser at 1.12 /spl mu/m with a 13-W pump at 1.07 /spl mu/m. Raman generation in optical fiber at a wavelength of 2.2 /spl mu/m was obtained for the first time.     

35-dB gain Tm-doped ZBLYAN fiber amplifier operating at 1.65 /spl mu/m

We demonstrate the first high gain rare-earth-doped fiber amplifier operating at 1.65 /spl mu/m. It consists of ZBLYAN fiber with a Tm/sup 3+/-doped core and Tb/sup 3+/-doped cladding, pumped by 1.22 /spl mu/m laser diodes. It is possible to achieve efficient amplification with Tm/sup 3+/ ions if their amplified spontaneous emission (ASE) in the 1.75 to 2.0 /spl mu/m wavelength region is suppressed by doping Tb/sup 3+/ ions in the cladding. A two-stage-type fiber amplifier is constructed and a signal gain of 35 dB is achieved for a pump power of 140 mW. A gain over 25 dB is realized in the 1.65 /spl mu/m to 1.67 /spl mu/m wavelength region.     

C-band emission from GaInNAsSb VCSEL on GaAs

The 1.55 /spl mu/m pulsed operation of an optically-pumped GaInNAsSb vertical-cavity surface-emitting laser (VCSEL) is reported. The structure employs a dielectric (SiO/sub 2//TiO/sub 2/) top mirror, while the bottom mirror and active region were grown on GaAs by MBE. Temperature-dependent (10-40/spl deg/C) laser measurements were made for an as-grown sample and an annealed sample, both having a room-temperature lasing wavelength of 1547 nm. Results indicate an annealing-induced blue-shift of the gain peak     

Efficient erbium-doped fibre amplifier pumped at 820 nm

The highest gain coefficients of 0.86 dB/mW at 1.552 mu m and 0.72 dB/mW at 1.534 mu m are realised at a pumping wavelength of 822 nm by using an erbium-doped fibre with a relative refractive index difference as high as 1.67%, a low intrinsic loss, and an erbium ion concentration of 210 p.p.m. The gains at 1.552 mu m reach 25 and 30 dB for launched pump powers of 30 and 40 mW, respectively.<>     

On a new topology for the transconductance feedback amplifier

A new topology for a transconductance feedback amplifier (TFA) is presented in this paper. The topology offers the advantage that it is capable of realizing the negative of the standard inverting gain expression. That is, gains of the form +R/sub 2//R/sub 1/. We will also show that it can realize the standard inverting and noninverting gains, all the while maintaining near constant bandwidth in each configuration as gain is varied. This first feature makes the proposed topology attractive for filtering applications since the TFA can function as an integrator, thereby allowing this amplifier to realize positive and negative lossless integrators. The proposed amplifier can also generate the logarithm of an input in the first and fourth quadrants, unlike previous TFA configurations. The proposed amplifier was verified experimentally for different gain configurations, integration and logarithmic capabilities by a chip designed using TSMC's 0.18-/spl mu/m CMOS process of a single ended power supply of 1.8 V. The chip occupied an area of 752.6 /spl mu/m by 581.2 /spl mu/m and contained the proposed amplifier and a conventional TFA for comparison purposes. A bandwidth of 15 MHz was observed for the proposed TFA in the unity gain (/spl plusmn/1) configuration.     

空芯波导用SiO2—TiO2—GeO2涂层的红外反射光谱分析

指出对于SiO2-TiO2凝胶玻璃涂层，即使TiO2含量高达80%，其对CO2激光波长(10.60μm）的IR反射率值仍很低。而对于SiO2-TiO2-GeO2涂层，当GeO2的含量从20%增加到30%时，其反射率峰逐步移向CO2激光波长，且在10.6μm处获得了20%的反射率。但当GeO2含量超过35%后，其IR反射率降低到几乎为零。因此，40SiO2-30TiO2-30GeO2的凝胶玻璃涂层是较理想的。     

Ultralong dispersion-shifted erbium-doped fiber amplifier and itsapplication to soliton transmission

Distributed, dispersion-shifted erbium-doped fiber amplifiers with doping concentrations as low as 0.1-0.5 p.p.m. (0.1-0.5×10^-4 wt.%) were fabricated and their grain characteristics studied for the purpose of soliton amplification. A 9.4-km dual-shape-core-type amplifier with a 0.5-p.p.m. concentration had a gain of more than 20 dB at 1.535 μm and 10 dB at 1.552 μm with a forward pumping configuration, and it could successfully amplify and transmit a 20-ps soliton pulse train at a 2.5-GHz repetition rate. The soliton transmission characteristics of an 18.2 km long fiber amplifier were studied using backward and forward pumping. It was found that A=1.5 soliton pulses with a pulse width of 20 ps could be amplified over 18.2 km at a repetition rate of 5 GHz, where soliton narrowing to 16 ps was observed     

1.65 /spl mu/m-band optical amplification with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping

In order to expand the available bandwidth for wavelength division multiplexing transmission systems, a 1.65 /spl mu/m-band optical fibre amplifier with Er/sup 3+/-doped fluorozirconate fibre using 0.8 /spl mu/m upconversion pumping has been demonstrated. The positive gain, 3.8 dB, is the first ever achieved by means of (/sup 2/H/sub 11/2/, /sup 4/S/sub 3/2/) /spl rarr/ /sup 4/I/sub 9/2/ stimulated emission transition.     

1.58-/spl mu/m broad-band erbium-doped tellurite fiber amplifier

This paper describes the development of a 1.58-/spl mu/m broad-band and gain-flattened erbium-doped tellurite fiber amplifier (EDTFA). First, we compare the spectroscopic properties of various glasses including the stimulated emission cross sections of the Er/sup 3+4/ I/sub 13/2/ /sup 4/I/sub 15/2/ transition and the signal excited-state absorption (ESA) cross sections of the Er/sup 3+4/ I/sub 13/2/ - /sup 4/I/sub 9/2/ transition. We detail the amplification characteristics of a 1.58-/spl mu/m-band EDTFA designed for wavelength-division-multiplexing applications by comparing it with a 1.58-/spl mu/m-band erbium-doped silica fiber amplifier. Furthermore, we describe the 1.58-/spl mu/m-band gain-flattened EDTFA we developed using a fiber-Bragg-grating-type gain equalizer. We achieved a gain of 25.3 dB and a noise figure of less than 6 dB with a slight gain excursion of 0.6 dB over a wide wavelength range of 1561-1611 nm. The total output power of the EDTFA module was 20.4 dBm and its power conversion efficiency reached 32.8%.     

Single-port laser-amplifier modulators for local access

We describe a single-port, reflective, waveguide modulator based on semiconductor laser amplifier technology. The single-port geometry reduces the high packaging cost associated with two-port waveguide modulators, while the internal gain of the amplifier compensates for splitting and coupling losses. A modulator with a bulk active layer showed a reflection-mode chip gain of 17 dB at /spl lambda/=1.56 /spl mu/m. When driven with pseudorandom digital data at 100 Mb/s, extinction ratios of >12 dB were observed over the broad wavelength range (20 nm) needed for wavelength division multiplexed systems. Bit-error-rate tests confirmed that there was no distortion penalty, compared to a LiNbO/sub 3/ reference modulator.     

Gain characteristics of an Er3+-doped multicomponentglass single-mode optical fiber

Experimental results on gain characteristics of an Er³⁺-doped multicomponent glass single-mode optical-fiber amplifier are reported. This amplifier shows a gain spectrum with twin gain peaks of 1.535 and 1.543 μm, providing a broadened gain bandwidth. The apparent 6-dB gain bandwidth is 12 nm. Furthermore, the signal gain of 17 dB and 15-mW pump power is realized at a signal wavelength of 1.536 μm, and a signal gain coefficient of 1.4 dB/mW is achieved