N. Tamchek

Double-pass L-band EDFA with enhanced noise figure characteristics

A new double-pass long wavelength band erbium-doped fiber amplifier with enhanced noise figure characteristics is demonstrated by adding a short length of forward pumped erbium-doped fiber (EDF) in front of a double-pass amplifier. Compared with the conventional double-pass amplifier, the new amplifier provides noise figure improvement of about 0.8 to 6.0 dB over the flat-gain region from 1568 to 1600 nm. Since the optical circulator prevents the amplified signal and backward amplified spontaneous emission from propagating into the EDF, the population inversion of the input part of the amplifier is hardly affected by the intense lights, therefore, the noise figure could be kept low. The new double-pass system has achieved a flat-gain output at about 33.5 dB, which is 13.5 dB higher than that of the single-pass system with gain variation less than 1.3 dB at the flat-gain region. The noise figure varies from 5.9 to 6.6 dB in this region.

Photonic Crystal Fiber in Photonic Crystal Fiber for Residual Dispersion Compensation Over

A photonic crystal fiber in photonic crystal fiber (PCF-in-PCF) architecture is numerically investigated for residual dispersion compensation in optical transmission link. The optimized structure shows a flattened and high average dispersion of -457.4 ps/nm/km in the wavelength range of 1360 nm to 1690 nm. The sensitivity of the fiber dispersion properties to a ±2% variation in the optimum parameters is studied for practical conditions. Additionally, the effect of variation in the structure parameters on effective mode area is simulated to understand its relationship to light confinement.

{\rm E} + {\rm S} + {\rm C} + {\rm L} + {\rm U}

We propose a wide angle, efficient and low loss 1 × 3 power splitter based on triangular lattice air holes silicon slab Photonic Crystal (PhC). Desired power splitting ratio was achieved by altering the structure at the junction area of the power splitter. Simulation results obtained using 2-D finite difference time domain method show that for TE polarization incident signal, the power is distributed almost equally with total normalized transmission of 99.74% and negligible reflection loss at the 1550 nm optical operating wavelength. In addition, the power splitter can operate at 1388 nm and 1470 nm optical wavelengths.

Wavelength Bands

A gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) with an improved gain characteristic is demonstrated by simply adding a broadband conventional band (C-band) fiber Bragg grating (FBG) in a two-stage amplifier system. The FBG reflects backward C-band amplified spontaneous emission (ASE) from the second stage back into the system to clamp the gain. The gain is clamped at about 22.4 dB with a gain variation below 0.4 dB for input signal powers of -40 to -15 dBm. Compared with an unclamped amplifier of similar noise figure values, the small signal gain has improved by 2.4 dB due to the FBG which blocks the backward propagating ASE. At wavelengths from 1570 to 1600 nm, gain of the clamped amplifier varies from 19.4 to 26.7 dB. The corresponding noise figure varies by /spl plusmn/0.35 dB around 5 dB, which is not much different compared to that of the unclamped amplifier.

Efficient, Wide Angle, Structure Tuned 1

Thermoluminescence (TL) flat optical fibers (FF) have been proposed as radiation sensor in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm3 contains pure silica SiO2 was selected for this research. The FF was annealed at 400°C for 1 h before irradiated. Kinetic parameters and dosimetric glow curve of TL response were studied in FF with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV using linear accelerator (LINAC) in the dose range of 2.0-10.0 Gy. The TL response was read using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80°C, maximum readout temperature is 400°C and the heating rate of 30°Cs-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used of LiF:MgTi dosimeter in medical radiotherapy application.

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Gain control in a long-wavelength (L-band) erbium-doped fiber amplifier (EDFA) using a counter-propagating ring resonator is demonstrated. The clamped gain can be controlled to be in the range from 7.0 to 18.0 dB for the 1580 nm signal at -30 dBm by tuning the oscillating laser in the range from 1565 to 1540 nm. The design prevents oscillating light from being coupled out, but it degrades the amplifiers noise figure and signal gain as the dynamic range is increased.

3 Photonic Crystal Power Splitter at 1550 nm for Triple Play Applications

The study on the optical properties of alkali borate glasses doped with rare earths is an interesting area of research. Dysporosium doped lithium magnesium borate glasses were prepared by melt-quenching technique with dysporosium concentration varying from 0.3 to 1.0 mol %. Physical and optical properties of Lithium Magnesium Borate doped with different concentration of Dy3+ were observed based on its physical parameters, emission spectra and absorption spectra. The absorption spectra of this study exhibits eight absorption bands with hypersensitive peak at 1260 nm (6H9/2). Two emitted spectra transitions were also observed at 4F9/2 → 6H15/2, 4F9/2 → 6H13/2. Lastly, important physical parameters for each concentration of dopant such as density, ions concentration, polaron radius, inter-nuclear distance, refractive index, oscillator strength and other parameters were determined.

Gain clamping in two-stage L-band EDFA using a broadband FBG

We propose a photonic crystal slab-based 1 × 3 power splitter with high output transmission and equal power distribution. It is designed by cascading an asymmetric 1 × 2 power splitter and a symmetric 1 × 2 power splitter. Desired equal power splitting is achieved by introducing and optimizing the splitting region of the 1 × 2 power splitters with flexible structural defects. Simulations were carried out by using 3-D Finite Difference Time Domain method showing equal normalized power distributions of 29.6%, 28.9% and 30.5% at 1550 nm optical wavelength. In addition, equal power splitting also takes place at 1561 nm.

Thermoluminescence characteristics of flat optical fiber in radiation dosimetry under different electron irradiation conditions

This paper reports the design, characterization and implementation of a Fiber Bragg Grating (FBG)-based temperature sensor for an Insulted-Gate Bipolar Transistor (IGBT) in a solar panel inverter. The FBG is bonded to the higher Coefficient of Thermal Expansion (CTE) side of a bimetallic strip to increase its sensitivity. Characterization results show a linear relationship between increasing temperature and the wavelength shift. It is found that the sensitivity of the sensor can be categorized into three characterization temperature regions between 26 °C and 90 °C. The region from 41 °C to 90 °C shows the highest sensitivity, with a value of 14 pm/°C. A new empirical model that considers both temperature and strain effects has been developed for the sensor. Finally, the FBG-bimetal temperature sensor is placed in a solar panel inverter and results confirm that it can be used for real-time monitoring of the IGBT temperature.

Gain Control in L-Band Erbium-Doped Fiber Amplifier Using a Ring Resonator

In this letter, a design of a gain-clamped long wavelength band erbium-doped fiber amplifier (L-band EDFA) is proposed using a fiber Bragg grating in a closed loop ring cavity. The design provides a clamping of the gain with different variable optical attenuator (VOA) losses varying from 0 to 12.5 dB. It is found that at 10 dB VOA loss, clamping of the gain is flat with variation of input power from -40 to -5 dBm. The gain measured is 10.9 dB, which is 30% less than the open ring gain of 15.3 dB at a pumping power of 92 mW. The noise figure measured is about 5.2 dB.