ASE Spectrum Research Articles

20 W 1952 nm tandem hybrid single and double clad TDFA

Abstract A simple engineering design is important for achieving high Thulium-doped amplifier (TDFA) performance such as good power conversion, low noise figure (NF), scalable output power, high gain, and stable operation over a large dynamic range. In this paper we report the design, performance, and simulation of two stage high-power 1952 nm hybrid single and double clad TDFAs. The first stage of our hybrid amplifier is a single clad design, and the second stage is a double clad design. We demonstrate TDFAs with an output power greater than 20 W with single-frequency narrow linewidth (i.e. MHz) input signals at both 1952 and 2004 nm. An optical 10 dB bandwidth of 80 nm is derived from the ASE spectrum. The power stage is constructed with 10 µm core active fibers showing a maximum optical slope efficiency greater than 50%. The experimental results lead to a 1 dB agreement with our simulation tool developed for single clad and double clad TDFAs. Overall this hybrid amplifier offers versatile features with the potential of much higher output power.

Solid state ASE from an oligomer (HOTF) in polymethyl methacrylate

Solid state laser material based on oligomer 9,9,9′,9′,9″,9″-hexakis(octyl)-2,7′,2′,7″-trifluorene (HOTF) doped poly methyl methacrylate (PMMA) was fabricated. The absorption spectrum showed only one band at 355 nm with different concentration ratios (7–12 mM); thus the broad absorption band could be attributed to the α-phase formation. In addition, there was no new band detected at the end of the spectrum as the concentration increased. This indicates the absence of the β-phase formation for all concentrations used. On the other hand, HOTF exhibited two distinct emission bands at 420 and 470 nm for 7 mM concentration. When the concentration was increased to 9 mM, the intensity of the band 470 nm increased. Further increase the concentration to 12 mM, the intensity of the band at 420 nm totally vanished and there was only one band at 470 nm. Therefore, the band at 470 could be attributed to excimer state. However, the results revealed that there is a strong correlation between quantum yield of fluorescence and fluorescence life-time, absorption cross section, and emission cross section. Under pulsed laser excitation. The ASE spectrum of HOTF has been obtained using a transverse cavity configuration where the conjugated HOTF was pumped by the third-harmonic of Nd:YAG nanosecond pulsed laser (λex = 355 nm). We demonstrate that HOTF in the solid state could produce an ASE peak at 420 nm. The obtained results were compared with the HOTF and a conducting polymer poly (9,9-dioctylfluorene) (PFO)in the liquid state.

Twenty two flattened channels L band multi-wavelength erbium doped fiber laser with composite ring cavity

We demonstrated the generation of a multiwavelength laser comb through two different ring cavity designs. The first design, a ring laser with Sagnac filter is being modified to produce a second design known as composite ring cavity. The ASE spectrum obtained from the composite ring cavity is sliced into more than 30 laser lines. From this comb, 22 laser lines are flattened under the 3 dB peak power fluctuation and 25 lines are flattened under the 10 dB peak power fluctuation. The 24 laser lines have a bandwidth value of 10.48 nm and for each of them, the average OSNR value is found to be at 24 dB. The OSNR value distribution among the laser lines is nearly uniform. However, the fineness obtained in this scheme is very low as 2.8.

Synthesis and spectroscopic properties of silica nanoparticles as scatter centers in random gain porous media

In this work, silica matrices have been synthesized and used as host for silica nanoparticles doped with Kiton Red laser dye using sol–gel technique. The bulk samples of KR–SiO2 nanoparticles confined in silica xerogel matrix have been prepared as a function of SiO2 nanoparticle sizes and concentrations. Different SiO2 particle sizes have been obtained by varying the pH value of starting silica precursor sol and determined using field emission scanning electron microscope. The structural characteristics of such matrices have been determined through FTIR spectra. Amplified spontaneous emission, threshold pumping energy, and mean free path for photons in the prepared random gain media have been reported. As a result, the best values of FWHM and threshold pumping energy, 8.7 nm and 12 mJ, have been observed for the sample prepared with 33.4 nm size and 2 wt% concentration of SiO2 nanoparticles. Comparison between the intensity of normal fluorescence spectrum (excited with CW laser diode 532 nm) and ASE spectrum (excited at 40 mJ pumping energy of 2nd harmonic Nd: YAG pulse laser 532 nm), Relation of both the bandwidth at FWHM and the peak fluorescence intensity as a function of pumping energy, Eth is the pumping threshold energy.

1.3mW 1550nm Er-DOPED SUPER FLUORESCENT FIBER SOURCE FOR MISSILE FIBER OPTICS GYROSCOPE

Single - axis missile fiber optic gyroscope requires a light source  with a band width> 10 nm and  output power > 0.5 mW  .The commercial FOGs   weigh  200-250gms with a physical size of 100mmX100mmX50mm..The type of light source for missile fiber optic gyroscope is selected by operating wavelength, wavelength stability with temperature, volume and physical size. Incase of space fiber gyroscopes, the source should be insensitive to high energy radiation like proton and gamma radiations as well. Large bandwidth light source contributes to small bias drift by gyroscope. A small volume and light weight Single Pass Backward Signal Er3+ doped Super-fluorescent Fiber source was developed using only four commercially available components for use in missile single axis fiber optic gyroscope .The bandwidth and output power of the source are 30. 507nm and1.318mW  respectively. We presented the experimental results along with non-flattened ASE spectrum. The packed super-fluorescent fiber  source   has   a volume of 100mm X 100mm X 25mm  and a weight of 150 grams which to our knowledge the  smallest  in volume and light in weight ever reported.

Development of 3.6 mW Er- doped C-band super fluorescent fiber source pumped at 980 nm

A 3.6mW single pass backward signal superfluorescent fiber source having a spectral width of 27.417nm was developed at a pump wavelength of 980.5nm and presented the experimental results along with non-flattened ASE spectrum. The fiber source could have direct applications in fiber sensors like fiber gyroscope or, in general, in any optical sensors in which a broad spectral band and high power source are required

Broadband ASE light source for 1800 nm wavelength region

The first ASE light source with a flat and broadband ASE spectrum in the 1800 nm wavelength region has been developed by combining a Tm3+-Tb3+-doped fibre and a Tm3+-doped fibre. The achieved bandwidth where the ASE intensity exceeded −20 dBm/nm was 162 nm (from 1690 to 1852 nm).

Morphopathological study of naturally occurring ovine pulmonary adenocarcinoma in sheep in Fars province, Iran.

Summary Ovine pulmonary adenocarcinoma (OPA) is a contagious and transmissible lung cancer of sheep resembling human bronchiolo-alveolar carcinoma. In the present study, lungs of 9400 sheep slaughtered in Fars province, Iran were examined morphopathologically. The OPA was diagnosed in the lungs of 21 (0.22%) out of 9400 sheep. Frequency of involvement of different lobes in the affected lungs was inclu ded apical lobe (62%), cardiac lobe (33%), middle lobe (33%), diaphragmatic lobe (62%) and accessory lobe (5%). In 12 sheep, the classical form observed as f irm, white to grayish coalescing masses mostly in t he cranio-ventral lobes associated with wet cut surfac e and frothy fluid in the airways. In 9 sheep, atyp ical lesions observed as small clearly demarcated nodule s mostly in diaphragmatic lobes associated with dry cut surface and minor fluid in the airways. Histopathol ogical changes were almost similar in the two forms . They consisted of an acinar or papillary growth of neopl astic cells in the alveoli and polypoid proliferati on of bronchiolar epithelium. There were variable amounts of connective tissue, myxomatous foci and infiltra tion of lymphocytes and plasma cells in the interstitial tissue of the affected alveoli. No metastatic lesi on was observed in the lymph nodes. The findings of this s tudy show that atypical and classical forms represe nt different stages or manifestations of a single dise ase spectrum.

PDL-Compensated Mechanically Induced Long-Period Grating for EDFA Gain Flattening

We present and demonstrate a polarization-insensitive mechanically induced long-period fiber grating (MLPG) for EDFA gain flattening. By forming a 90° fiber rotator in the middle of the MLPG the PDL of the MLPG was substantially reduced. The PDL-compensated MLPG was able to flatten the ASE spectrum of an EDFA successfully without deterioration of the polarization characteristics.

Characteristics of the erbium doped fiber amplifier with polarization mode dispersion compensation

We have experimentally demonstrated the characteristics of the reflective type erbium-doped fiber amplifier (R-EDFA) which is composed of a circulator and a Faraday rotator mirror. It is shown that the gain spectrum of the R-EDFA is shifted to longer wavelength when compared with that of the conventional single-pass EDFA. For the R-EDFA, the forward pumping is better than the backward pumping in gain and noise figure. Besides, the reflective structure can be used as a broad band light source because its ASE spectrum is wider and the output power is higher. We also show that, by using the reflective type configuration, the polarization dependent gain is reduced and the polarization mode dispersion of EDF can be completely compensated but the polarization mode dispersion from the circulator is still survived.

Wavelength conversion based on cross-gain modulation of ASE spectrum of SOA

We propose and demonstrate a simple and new scheme of wavelength conversion in which the cross-gain modulation of amplified spontaneous emission of a semiconductor optical amplifier is used to convert the pump signal wavelength by means of the spectrum-spliced method. This technology allows pump wavelength to be converted into any other wavelength without using any probe light source.

Adaptive gain equalizer in high-index-contrast SiON technology

An adaptive gain equalization filter is presented. The filter is based on the resonant coupler principle, a cascade of power couplers and delay lines. Reconfigurability and tuning is achieved by varying coupling strength and delay line length via the thermo optic effect. A device consisting of seven delay line stages was realized in high-index-contrast silicon-oxynitride technology. This device flattens the ASE spectrum of an EDFA to a ripple of less than 0.5 dB over 35 nm. The on-chip losses are 2 dB.

IMPACT OF ASE NOISE OF OPTICAL AMPLIFIER ON PIN-RECEIVER AND CALCULATION OF BIT-ERROR RATE

A simple analytical expression is derived to calculate the Bit-Error Rate in lightwave systems with optical amplifiers. According to this expression the Bit-Error Rate can be estimated by the signal power and the ASE spectrum density before the receiver. The theoretical calculation agrees with the experiment very well, so it can provide a method to judge the quality of the optical channel in the optical communication system with optical amplifiers. Futhermore, the impact of the ASE noise on the receiver sensitivity is discussed. It is important to select proper receivers in practical systems.

Wideband gain flattened erbium fibre amplifier using a photosensitive fibre blazed grating

An erbium fibre amplifier with a highly flattened gain spectrum is demonstrated for the first time using an all fibre photosensitive Bragg grating. An ASE spectrum flattened to within ±0.5 dB over a bandwidth of 35 nm in the 1550 nm window is achieved with a 3 mm long radiation coupling Bragg fibre grating.