A low-noise and gain-flattened amplifier composed of a silica-based and a fluoride-based Er/sup 3+/-doped fiber amplifier in a cascade configuration

We propose a novel low noise and gain-flattened Er/sup 3+/-doped fiber amplifier (EDFA) with a cascade configuration for wavelength division multiplexing (WDM) signals. In this configuration, a 1480-nm pumped fluoride-based EDFA is joined to a 980-nm pumped silica-based EDFA through an optical isolator. By adjusting the silica-based Er/sup 3+/-doped fiber length in the silica-based EDFA, we realized an excellent flat gain EDFA with a gain excursion of less than 0.9 dB and noise figure of 5.7/spl plusmn/0.2 dB, and a low noise EDFA with a noise figure of 5/spl plusmn/0.2 dB and a gain excursion of less than 1.4 dB, for 8 channel WDM signal in the 1532-1560-nm wavelength region.     

WDM EDFA gain characterization with a reduced set of saturating channels

The advent of EDFA-based dense WDM places demanding optical source requirements for EDFA characterization. An iterative method is proposed here, based on a homogeneous amplifier model, to calculate the required signal conditions for WDM testing with a reduced set of saturating channels and a broad-band noise probe. EDFA gain measurements demonstrating this reduced-source technique agree to within 0.2 dB to those obtained with a four-channel WDM system operating near 1.55 /spl mu/m.     

1.49-/spl mu/m-band gain-shifted thulium-doped fiber amplifier for WDM transmission systems

This paper describes in detail the amplification characteristics of gain-shifted thulium-doped fiber amplifiers (GS-TDFAs) operating in the 1480to 1510-nm wavelength region (1.49-/spl mu/m S-band) for use in wavelength-division-multiplexing (WDM) systems. Gain shifting of a TDFA, which normally has a gain band at 1.47 /spl mu/m (S/sup +/-band), is achieved by two types of dual-wavelength pumping: (1) 1.05 and 1.56 /spl mu/m or (2) 1.4 and 1.56 /spl mu/m. The main pump source at 1.05 or 1.4 /spl mu/m creates population inversion between /sup 3/F/sub 4/ (upper laser level) and /sup 3/H/sub 4/ (lower laser level), while the auxiliary pump source at 1.56 /spl mu/m reduces the average fractional inversion down to approximately 0.4, which is a desired level for gain shifting. We show experimentally that the former provides a low internal noise figure (<4 dB) due to high fractional inversion at the input end of a thulium fiber, while the latter provides a very high optical efficiency but a higher internal noise figure (/spl sim/5 dB) due to the lower fractional inversion at the input end. These characteristics were verified by numerical simulation based on a comprehensive rate equation modeling. We demonstrated a 1.4- and 1.56-/spl mu/m laser-diode-pumped GS-TDFA with an optical efficiency of 29.3% and high output power of +21.5 dBm. Gain flatness and tilt control were also investigated. These results strongly confirm the feasibility of using GS-TDFAs in practical ultralarge-capacity WDM networks.     

A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-/spl mu/m operation

A novel ultracompact 2/spl times/2 wavelength division multiplexer (WDM) for 1.55-/spl mu/m operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 /spl mu/m. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 /spl mu/m which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved.     

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.     

A W-band InAs/AlSb low-noise/low-power amplifier

The first W-band antimonide based compound semiconductor low-noise amplifier has been demonstrated. The compact 1.4-mm/sup 2/ three-stage co-planar waveguide amplifier with 0.1-/spl mu/m InAs/AlSb high electron mobility transistor devices is fabricated on a 100-/spl mu/m GaAs substrate. Minimum noise-figure of 5.4dB with an associated gain of 11.1 dB is demonstrated at a total chip dissipation of 1.8 mW at 94 GHz. Biased for higher gain, 16/spl plusmn/1 dB is measured over a 77-103 GHz frequency band.     

A low-voltage folded-switching mixer in 0.18-/spl mu/m CMOS

Scaling of CMOS technologies has a great impact on analog design. The most severe consequence is the reduction of the voltage supply. In this paper, a low voltage, low power, AC-coupled folded-switching mixer with current-reuse is presented. The main advantages of the introduced mixer topology are: high voltage gain, moderate noise figure, moderate linearity, and operation at low supply voltages. Insight into the mixer operation is given by analyzing voltage gain, noise figure (NF), linearity (IIP3), and DC stability. The mixer is designed and implemented in 0.18-/spl mu/m CMOS technology with metal-insulator-metal (MIM) capacitors as an option. The active chip area is 160 /spl mu/m/spl times/200 /spl mu/m. At 2.4 GHz a single side band (SSB) noise figure of 13.9 dB, a voltage gain of 11.9 dB and an IIP3 of -3 dBm are measured at a supply voltage of 1 V and with a power consumption of only 3.2 mW. At a supply voltage of 1.8 V, an SSB noise figure of 12.9 dB, a voltage gain of 16 dB and an IIP3 of 1 dBm are measured at a power consumption of 8.1 mW.     

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%.     

Development of multiband phase shifters in 180-nm RF CMOS technology with active loss compensation

We present the design and development of a novel integrated multiband phase shifter that has an embedded distributed amplifier for loss compensation in 0.18-/spl mu/m RF CMOS technology. The phase shifter achieves a measured 180/spl deg/ phase tuning range in a 2.4-GHz band and a measured 360/spl deg/ phase tuning range in both 3.5- and 5.8-GHz bands. The gain in the 2.4-GHz band varies from 0.14 to 6.6 dB during phase tuning. The insertion loss varies from -3.7 dB to 5.4-dB gain and -4.5 dB to 2.1-dB gain in the 3.5- and 5.8-GHz bands, respectively. The gain variation can be calibrated by adaptively tuning the bias condition of the embedded amplifier to yield a flat gain during phase tuning. The return loss is less than -10 dB at all conditions. The chip size is 1200 /spl mu/m/spl times/2300 /spl mu/m including pads.     

Highly efficient optical fibre amplifier pumped by a 0.8 mu m band laser diode

A highly efficient Er-doped fibre amplifier pumped by GaAlAs laser diodes is reported. Using a low Er-cluster content fibre with a high numerical aperture, the EDFA attains 39 dB signal gain for double LD pumping and 30 dB for single LD pumping at 1.536 mu m. A maximum gain coefficient of 1.3 dB/mW was achieved at the 0.827 mu m pump band.<>     

High-power 1.3-/spl mu/m InGaAsP-InP amplifiers with tapered gain regions

Tapered structures fabricated in InGaAsP-InP 1.3-/spl mu/m quantum-well material have been evaluated as high-gain high-saturation-power amplifiers. The devices, which had a 1-mm-long ridge-waveguide input gain section followed by a 2-mm-long tapered section, demonstrated an unsaturated gain of 26 dB at 2.0 A and about 30 dB at 2.8 A. Saturated output power at 2.8 A was >750 mW. At 2.0-A drive current and /spl ap/10-mW input power, the relative intensity noise of the amplified signal was /spl les/-160 dB/Hz at frequencies /spl ges/2 GHz.     

Plug-in type 1.3-/spl mu/m fiber amplifier module for rack-mounted shelves

We have successfully developed a plug-in type PDFA module for rack mounted shelves which is assembled on a printed-board. In this module, we use a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber and wavelength stabilized 1.017-/spl mu/m laser diodes (LDs). We have obtained a small-signal gain of 24 dB and a noise figure of 6.6 dB at 1.30 /spl mu/m with an LD drive current of 240 mA/spl times/2. We achieved an output power of 10 dBm with a signal input power of 0 dBm. The total power consumption of this module, including that of a Peltier cooler, was 3.5 W when the LD drive current was 240 mA/spl times/2.     

Experimental characterization of a dynamically gain-flattened erbium-doped fiber amplifier

We have designed and experimentally characterized an erbium doped fiber amplifier (EDFA) which possesses a wavelength-independent gain spectrum, independent of the operating level of the gain (dynamic gain flatness), and without requiring any gain-level-dependent control of any parameters. In the wavelength range 1542-1552 nm, the gain was flat to within the experimental uncertainties of /spl plusmn/0.3 dB even as the gain level changed by 17 dB. The EDFA was based on a low-Al-content alumino-germanosilicate EDF and a Mach-Zehnder filter. We believe that this type of EDFA, which has not been demonstrated before, can significantly simplify the design of amplified wavelength-division multiplexing (WDM) transmission systems and increase the robustness of long-distance WDM transmission.     

17-GHz 50-60 mW power amplifiers in 0.13-/spl mu/m standard CMOS

Two versions of power amplifiers with different output matching approaches for the 17-GHz band were realized in 0.13-/spl mu/m standard digital CMOS technology with 1.5-V supply voltage. The power amplifier with an external matching network delivers 17.8-dBm saturated output power with 15.6% power added efficiency (PAE). The small-signal gain is 11.5 dB. The fully integrated power amplifier delivers 17.1-dBm saturated output power with 9.3% PAE. The small-signal gain is 14.5 dB. No external radio frequency components are required.     

All-optical gain control of in-line erbium-doped fiber amplifiers for hybrid analog/digital WDM systems

Automatic gain control using an all-optical feedback loop in in-line erbium-doped fiber amplifiers (EDFA's) used in hybrid analog/digital wavelength division multiplexing (WDM) systems was studied. It is found that the signal level variation for the digital channels can be maintained within a range /spl les/3-dB between the presence and dropout of the analog channel when the narrowband feedback is centered at the amplified spontaneous emission (ASE) peak (/spl sim/1532 nm) with loop loss ranging between 13-22 dB. Robust transmission at 2.5 Gb/s without measurable power penalty was obtained for the digital channels when the EDFA was saturated by either the analog or the control lasing signal.     

Low-noise metamorphic HEMTs with reflowed 0.1-/spl mu/m T-gate

A 0.1-/spl mu/m T-gate fabricated using e-beam lithography and thermally reflow process was developed and applied to the manufacture of the low-noise metamorphic high electron-mobility transistors (MHEMTs). The T-gate developed using the thermally reflowed e-beam resist technique had a gate length of 0.1 /spl mu/m and compatible with the MHEMT fabrication process. The MHEMT manufactured demonstrates a cutoff frequency f/sub T/ of 154 GHz and a maximum frequency f/sub max/ of 300 GHz. The noise figure for the 160 /spl mu/m gate-width device is less than 1 dB and the associated gain is up to 14 dB at 18 GHz. This is the first report of a 0.1 /spl mu/m MHEMT device manufactured using the reflowed e-beam resist process for T-gate formation.     

A K-band down-conversion mixer with 1.4-GHz bandwidth in 0.13-/spl mu/m CMOS technology

A low power and low voltage down conversion mixer working at K-band is designed and fabricated in a 0.13/spl mu/m CMOS logic process. The mixer down converts RF signals from 19GHz to 2.7GHz intermediate frequency. The mixer achieves a conversion gain of 1dB, a very low single side band noise figure of 9dB and third order intermodulation point of -2dBm, while consuming 6.9mW power from a 1.2V supply. The 3-dB conversion gain bandwidth is 1.4GHz, which is almost 50% of the IF. This mixer with small frequency re-tuning can be used for ultra-wide band radars operating in the 22-29GHz band.     

A 5.7-GHz 0.18-/spl mu/m CMOS gain-controlled differential LNA with current reuse for WLAN receiver

This letter presents a 5.7 GHz 0.18 /spl mu/m CMOS gain-controlled differential LNA for an IEEE 802.11a WLAN application. The differential LNA, fabricated with the 0.18 /spl mu/m 1P6M standard CMOS process, uses a current-reuse technology to increase linear gain and save power consumption. The circuit measurement is performed using an FR-4 PCB test fixture. The LNA exhibits a noise figure of 3.7 dB, linear gain of 12.5 dB, P/sub 1dB/ of -11 dBm, and gain tuning range of 6.9 dB. The power consumption is 14.4 mW at V/sub DD/=1.8 V.     

A 10-Gb/s receiver with series equalizer and on-chip ISI monitor in 0.11-/spl mu/m CMOS

A 10-Gb/s receiver is presented that consists of an equalizer, an intersymbol interference (ISI) monitor, and a clock and data recovery (CDR) unit. The equalizer uses the Cherry-Hooper topology to achieve high-bandwidth with small area and low power consumption, without using on-chip inductors. The ISI monitor measures the channel response including the wire and the equalizer on the fly by calculating the correlation between the error in the input signal and the past decision data. A switched capacitor correlator enables a compact and low power implementation of the ISI monitor. The receiver test chip was fabricated by using a standard 0.11-/spl mu/m CMOS technology. The receiver active area is 0.8 mm/sup 2/ and it consumes 133 mW with a 1.2-V power supply. The equalizer compensates for high-frequency losses ranging from 0 dB to 20 dB with a bit error rate of less than 10/sup -12/. The areas and power consumptions are 47 /spl mu/m /spl times/ 85 /spl mu/m and 13.2 mW for the equalizer, and 145 /spl mu/m /spl times/ 80 /spl mu/m and 10 mW for the ISI monitor.     

An ultrawideband CMOS low-noise amplifier for 3.1-10.6-GHz wireless receivers

An ultrawideband 3.1-10.6-GHz low-noise amplifier employing an input three-section band-pass Chebyshev filter is presented. Fabricated in a 0.18-/spl mu/m CMOS process, the IC prototype achieves a power gain of 9.3 dB with an input match of -10 dB over the band, a minimum noise figure of 4 dB, and an IIP3 of -6.7 dBm while consuming 9 mW.