Broadband Incoherent Source Research Articles

High-Bit-Rate Dense SS-WDM PON Using SOA-Based Noise Reduction With a Novel Balanced Detection

The major drawback of incoherent broadband sources (BBSs) is their inherent intensity noise. Semiconductor optical amplifiers (SOAs) can be exploited at the transmitter to mitigate this noise. Optical filtering at the receiver, however, leads to the return of most of suppressed noise. Wider filtering at the receiver is the best known strategy to maintain performance gains, at the price of reduced spectral efficiency due to the tradeoff between noise cleaning and adjacent channel crosstalk. We introduce a novel balanced receiver for wavelength division multiplexing (WDM) systems that maintains greater noise cleaning and leaves spectral efficiency unchanged. Unlike standard receivers, our balanced scheme does not filter the desired signal. In this paper, we first demonstrate that the newly proposed receiver is equivalent to standard WDM receivers when no SOA for noise cleaning is present at the transmitter. Although a 2.9-dB power penalty is incurred, network capacity is unchanged, i.e., bit error rate (BER) floors due to intensity noise are the same. When SOAs are employed to mitigate severe intensity noise, we show that our receiver outperforms the wide filtering strategy by two orders of magnitude. Dense WDM capacity is demonstrated up to 10 Gb/s using a thermal source, a saturated SOA, and the balanced detection scheme. A BER of 10-6 is achieved at 10 Gb/s; further improvement is possible using low overhead forward error correction or a better SOA design. This demonstrates the ability of spectrum-sliced wavelength division multiplexing (SS-WDM) passive optical networks (PONs) to operate at 10 Gb/s at good spectral efficiency. Error performance better than 10-9 is achieved up to 8 Gb/s with 30-GHz optical channel bandwidth and 100-GHz spacing.

Monochromatic microwave radiation from the system of strongly excited magnons

A conversion of a broadband microwave energy accumulated by a system of strongly excited magnons into a monochromatic microwave is demonstrated. The mechanism is based on recently discovered room-temperature Bose–Einstein condensation of nonequilibrium magnons. A realization of an electronically tunable microwave generator pumped by an incoherent broadband sources and the achievable linewidth of the monochromatic radiation are discussed.

Asymptotic properties of incoherent waves propagating in an all-optical regenerators line

We present an original method to generate optical pulse trains with random time-interval values from incoherent broadband sources. More precisely, our technique relies on the remarkable properties of a line made of cascaded self-phase modulation-based optical regenerators. Depending on the regenerator parameters, various regimes with noticeably different physical behaviors can be reported.

Experimental verification and capacity prediction of FE-OCDMA using superimposed FBG

This paper presents the experimental demonstration and simulation results of a frequency-encoded optical code-division multiple-access (FE-OCDMA) system using broad-band incoherent source, superimposed fiber Bragg gratings for encoding/decoding of unipolar m-sequence codes, and balanced detection. The bit-error rate is measured for up to four simultaneous users at 155 and 622 Mb/s. Exploiting the excellent match between simulation and experiment, the paper concludes with a prediction of the potential capacity of an optimized FE-CDMA system.

Optimum Configuration and Design of L-Band Erbium-Doped Superfluorescent Fiber Source

This paper investigates the design and optimum configuration of 1480 nm pumped high-power L-band (1570–1610 nm) erbium-doped superfluorescent fiber sources (SFSs). These broadband incoherent sources may find important applications in such areas as sliced wavelength-division multiplexed (WDM) local-access networks, characteristic measurement for dense WDM components, laser spectroscopy, and fiber-optic sensor systems. We theoretically investigated and compared the characteristics of SFSs in terms of the mean wavelength, output power, and for various configurations of single-pass forward (SPF), single-pass backward (SPB), double-pass forward (DPF), and double-pass backward (DPB) structures. Among these configurations, the DPF scheme offered the highest output power with a good flat spectrum for an L-band fiber source. Both SPF and SPB configurations failed to implement the L-band SFSs. Though the DPB configuration could offer L-band SFS output power, the flat spectrum profile was difficult to establish. The results of this study may provide the configuration selection and design criteria of L-band erbium-doped SFSs.

Infrared laser single photon absorption reaction chemistry in the solid state. I. The system SiH4–UF6 a)

The reaction between SiH4 and UF6 under thermal gas phase and photon initiated conditions in cryogenic matrices has been investigated. The gas phase thermal reaction begins at 130–140° C producing HF, SiH3F, and a solid uranium fluoride product. When the UF6 is matrix isolated within SiH4 at 12 K and exposed to low power infrared radiation of 25 mW cm−2 using laser emissions resonant with the ν3 band of UF6, a reaction also occurs. This reaction produces SiH3F, UF5, and UF4 as products. The same reaction is also catalyzed using a broad band incoherent source with a photon flux density of 10 μW cm−2. The activation energy for the photoreaction (1.8 kcal mol−1) is considerably lower than the thermal activation barrier for the gas phase reaction. These experiments are part of the bases for uncovering a process of photochemistry of reactants in fixed relative configurations–single photon absorption reaction chemistry in the solid state (SPARCSS). This process is a manifestation of a previously unrecognized, general matrix phenomenon in which spatial configurations dramatically affect potential energy surfaces for reaction.

Quantum-Mechanical Effects in Stimulated Optical Emission. II

The existence of multiple-quantum transitions in optically pumped lasers, along with splitting of the laser line due to the modulation of the wave function at an angular frequency determined by the rate of pumping, is demonstrated for a certain class of incoherent broad-band sources pumping large pump bands in crystals. The source consists of a large number of stationary elements emitting wave fields continuously at various arbitrary frequencies and arbitrary phases. The distribution of frequencies and phases among the various elements is random. The pump band belongs to the class found in laser crystals of the ionic type. The analysis shows that such sources pumping such bands act like narrow-line sources pumping narrow lines. The effective linewidth is directly related to the pump rate.