High-gain, high-power 1.3 μm compressive strained MQW opticalamplifier

A high-gain and high-saturation output power optical amplifier operating in the 1.3-μm wavelength region that was fabricated using a compressive-strained multiple-quantum-well active region is described. It is shown that optical gain as high as 27 dB and 3-dB saturation output power as high as 14 dBm were obtained simultaneously     

High-gain polarization-insensitive optical amplifier

A polarization-insensitive optical amplifier (PIOA) consisting of two serial semiconductor laser amplifiers (SLAs) is studied theoretically and experimentally. A polarization-insensitive isolator (PII) inserted between the two SLAs serves not only to eliminate the coupling cavity, but also to rotate any polarized forward light by 90°. Experimental results show a maximum fiber-to-fiber gain of 29 dB. PIOA gain deviation for the input polarization launch angle is just 0.6 dB compared to an original value of 5-6 dB in a single SLA. A theoretical analysis shows that it is necessary to achieve a PII rotation design error of less than 0.5° in order to suppress deviation below 0.1 dB. PIOA noise figure deviation, for the input signal polarization launch angle, was only 0.1 dB from both the experimental and theoretical results even though there was a rotation error of 2°     

High-gain mode-adapted semiconductor optical amplifier with12.4-dBm saturation output power at 1550 nm

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 2³¹ -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10^-11     

All-optical 1300-nm to 1550-nm wavelength conversion using cross-phase modulation in a semiconductor optical amplifier

All-optical 1300-nm to 1550-nm wavelength converters may be important components in lightwave networks which use both the 1300-nm and the 1550-nm low-loss transmission windows of silica optical fiber. We describe a new all-optical 1300-nm to 1550-nm wavelength converter, based on cross-phase modulation in a 1300-nm semiconductor optical amplifier. We demonstrate operation of the wavelength converter at 1.25 Gb/s, and present bit-error rate measurements. The wavelength converter demonstrated here potentially operates at high speed, with low input power and low polarization-sensitivity.     

Polarization-insensitive optical amplifier withtensile-strained-barrier MQW structure

A new approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of a tensile-strained-barrier MQW structure that enhances TM mode gain. Polarization sensitivity below 0.5 dB is realized at a wavelength of 1.56 μm. A signal gain of 27.5 dB is obtained along with a saturation output power of 14 dBm. Deriving the refractive indices of well and barrier layers from both experiment and theory, we succeed in separation of the effect of the confinement factor and the gain coefficient. It is determined that TM mode gain enhancement in this structure is primarily due to the increase in the confinement factor     

1550-nm volume holography for optical communication devices

The two-lambda method can provide a strategic approach to implement all-optical devices for communication wavelength division multiplexing (WDM) signal processing based on volume holography. By writing holograms at 488 nm in LiNbO/sub 3/:Fe and reading them in the third window of optical communication systems (1550 nm), the feasibility of WDM demultiplexers and holographic memories for digital bytes is here demonstrated.     

High-gain quantum-dot semiconductor optical amplifier for 1300 nm

Using an AlGaAs-GaAs waveguide structure with a six-stack InAs-InGaAs "dots-in-a-well" (DWELL) gain region having an aggregate dot density of approximately 8/spl times/10/sup 11/ cm/sup -2/, an optical gain of 18 dB at 1300 nm has been obtained in a 2.4-mm-long amplifier at 100-mA pump current. The optical bandwidth is 50 nm, and the output saturation power is 9 dBm. The dependence of the amplifier parameters on the pump current and the gain recovery dynamics has also been studied.     

Single frequency 1550-nm AlGaInAs-InP tapered high-power laser witha distributed Bragg reflector

A strained-layer multiple-quantum-well tapered laser with single-frequency operation near 1550 nm and with 20-dB sidemode suppression, for continuous-wave power levels up to 0.6 W is reported. At a power level of 0.5 W, 80% of the power from this device remains in the central lobe of the far-field. Increased lateral mode stabilization was observed in devices having both a Gaussian-patterned contact and a distributed Bragg reflector (DBR) compared to those without a DBR. An increase by a factor of five in the power level obtainable, with at least 80% of that power in the central lobe of the far-field pattern, was obtained using the DBR reflector     

High-gain 1310-nm reflective semiconductor optical amplifiers with low-gain uncertainty

A 1310-nm reflective semiconductor optical amplifier with a gain uncertainty of only 0.8 dB at an average gain level of over 30 dB has been demonstrated using a microoptic polarization reversing retroreflector. For this amplifier 3-dB saturation output powers of up to 10 dBm and a noise figure of 7.5 dB have been obtained. A low gain uncertainty for undefined input signal polarization states and input signal wavelengths (which may vary over several nanometers) is of primary importance in switching applications.     

Integrated MQW optical amplifier/noise-filter/photodetectorphotonic circuit

A monolithically integrated photonic circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier, a Bragg reflection grating-folded noise filter, and an MQW photodetector has been demonstrated. This photonic circuit offers potential as a preamplified lightwave receiver in high-data-rate applications because of its compactness and potentially low cost     

1.55 mu m polarization-insensitive high-gain tensile-strained-barrier MQW optical amplifier

A polarization-insensitive semiconductor optical amplifier was realized at a wavelength of 1.55 mu m. The active layer consisted of a tensile-strained-barrier multiple quantum well (MQW) structure. At a driving current of 150 mA, no dependence of the saturation characteristics on modes was obtained. The saturation output power at which the gain decreases 3 dB is 13.3 dBm. A slightly higher saturation output power of 14 dBm was measured at a driving current of 200 mA. No large difference was observed between transverse-electric (TE) and transverse-magnetic (TM) modes. A high gain of 27.5 dB at a polarization sensitivity of 0.5 dB and a high saturation output of 14 dBm were realized simultaneously by using a longer device with reduced residual facet reflectivities.<>     

1310-nm DBR-type MQW gain-clamped semiconductor optical amplifiers with AM-CATV-grade linearity

A 1310-nm gain clamped semiconductor optical amplifier with amplitude modulation CATV-grade linearity at an output power of 8 mW is demonstrated for the first time. The InGaAsP multiquantum-well laser amplifier is equipped with distributed Bragg reflectors at each end to supply the feedback necessary for gain clamping. The TE optical gain of 21.3 dB is measured to be constant within 0.1 dB up to 25-mW signal output power. Electrical signal distortion experiments are presented to demonstrate the linearity of the device.     

Rayleigh backscatter effects on 1550-nm CATV distribution systemsemploying optical amplifiers

We analyzed the applicability of externally modulated 1550-nm laser transmitters for trunking and distribution of AM CATV channels using power and in-line EDFA's. The distribution of multiple AM CATV channels over long fiber spans is degraded by the presence of Rayleigh backscatter-induced low-frequency interferometric noise. When the laser source is modulated externally, the low-frequency interferometric noise is mixed and translated around the AM carriers. Furthermore, when isolators are not used with the optical amplifiers, the low end of the broadcast channels could be severely degraded due to doubly amplified Rayleigh backscatter. Employing narrow-linewidth semiconductor or Nd:YAG laser sources at the transmitter will lower the tail of the low-frequency interferometric noise level but will increase the translated noise peak level at each AM carrier. Therefore, the standard CNR measurement techniques, which assumes the noise spectrum is flat, may not reveal the correct video picture quality seen at the customer premises. In this analysis, we compared NCTA RF CNR and baseband video SNR results using CCIR recommended unified weighting filter. We determined that for laser linewidth less than 1 MHz and with long fiber spans, baseband video SNR as opposed to RF CNR measurements should be used to characterize the performance of AM-VSB CATV broadcast distribution systems. Finally, an experimental 78-channel AM-VSB CATV distribution system is constructed employing two EDFA's simulating head-end and hub sites and we compared RF CNR and baseband video SNR measurements using a 700-kHz linewidth externally modulated 1550-nm DFB transmitter     

InGaAs/InGaAsP MQW optical amplifier integrated withgrating-assisted vertical-coupler noise filter

A photonic integrated circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier and a grating-assisted vertical-coupler filter as a noise filter have been demonstrated. A fiber-to-amplifier/filter gain of ~0.5 dB and a 3-dB filter bandwidth (FWHM) of ~70 Å at 1.56 μm filter center wavelength have been achieved. This photonic circuit is potentially suitable as a building-block for preamplifier lightwave receivers or high-gain, high-power optical amplifiers which are essential for optical communication systems and lightwave networks     

Gain tilt control of L-band erbium-doped fiber amplifier by using a1550-nm band light injection

In this letter, we demonstrate a new method to control gain tilt in long wavelength erbium-doped fiber amplifiers by using an external light source in 1550-nm range (called control source). The wavelength or its input power is adjusted to reduce gain tilt. The tilted gain is diminished from 7.18 to 0.07 dB by adjusting control source wavelength, and from 9.95 to 0.62 dB by adjusting control source input power in a 1570-1590-nm signal wavelength range     

High-gain,high-bandwidth,rail-to-rail,constant-gm CMOS operational amplifier

This study presents a high-gain, high-bandwidth, constant-g_m , rail-to-rail operational amplifier (op-amp). The constant transconductance is improved with a source-to-bulk bias control of an input pair. A source degeneration scheme is also adapted to the output stage for receiving wide input range without degradation of the gain. Additionally, several compensation schemes are employed to enhance the stability. A test chip is fabricated in a 0.18?µm complementary metal-oxide semiconductor process. The active area of the op-amp is 181?×?173?µm² and it consumes a power of 2.41?mW at a supply voltage of 1.8?V. The op-amp achieves a dc gain of 94.3?dB and a bandwidth of 45?MHz when the output capacitive load is connected to an effective load of 42.5?pF. A class-AB output stage combining a slew rate (SR) boost circuit provides a sinking current of 6?mA and an SR of 17?V/µs.     

Design and ASE characteristics of 1550-nm polarization-insensitivesemiconductor optical amplifiers containing tensile and compressivewells

The polarization dependence of 1550-nm semiconductor optical amplifiers (SOA's) containing tensile and compressive wells has been investigated both theoretically and experimentally. Our model to predict the polarization-resolved (TE and TM) gain spectra of these structures has been confirmed by amplified spontaneous emission measurements. It is found that there can be appreciable carrier redistribution between the two types of wells when the tensile layers have the large thickness (greater than 100 Å) needed for gain at wavelengths around 1550 nm. This carrier redistribution can significantly modify the ratio of the gains for different polarizations, in particular, decreasing the TM gain with respect to the TE gain, and, hence, is an important design consideration. We use our model and experimental data to explore design criteria for 1550-nm polarization-independent SOA's     

A microstructure-fiber-based 10-GHz synchronized tunable optical parametric oscillator in the 1550-nm regime

We demonstrate a microstructure-fiber (MF)-based supercontinuum source and a synchronously pumped optical parametric oscillator in the 1550-nm regime. By using a 12.5-m-long MF, we obtained a 10-GHz repetition-rate picosecond-pulse source that is capable of /spl sim/120-nm wavelength tunability due to the wide-gain bandwidth of the combined processes of stimulated Raman scattering and parametric four-wave mixing.     

High-gain 1310 nm semiconductor optical amplifier modules with a built-in amplified signal monitor for optical gain control

A compact high-gain 1310-nm semiconductor optical amplifier (SOA) module incorporating two photodiodes to detect radiation emitted from the two opposite facets of the amplifier chip is reported. By subtracting their signals, a measure of the amplified signal is obtained without the need for optical filtering, Using this, amplified signals can be stabilized within 0.5 dB over a 25-dB range of input signals.