A thulium-doped (Tm3+) optical fiber amplifier (TDFA) module operating in the E-band is proposed. The bandwidth limitation inherent in E-band amplifiers employing rare-earth element doping is mitigated through the utilization of the amplifier module designed with a parallel combination of the two TDFAs. The performance of the amplifier is effectively analyzed through the optimization of parameters including TDF length, Tm3+ density, doping-radius of Tm3+, numerical aperture, and input signal power to the TDFAs. An average gain of 37.12 dB and a noise figure <3.93 dB are obtained in the wavelength region of 1412 to 1460 nm with a maximum of 41.54 dB at 1432 nm having a moderately uniform gain. The impact of the nonlinear ion–ion interaction mechanism (IM) on the signal is also investigated for the designed amplifier module. Having obtained the optimized parameter set, the percentage increase of 0.029% and decreases of 0.043% in the signal gain at the wavelengths of 1420 and 1448 nm, respectively, are obtained considering the IM effects.
We present the effect of losses and nonlinearity on the behavior of modulation instability (MI) in thulium-doped fiber amplifier (TDFA) operational in S and near-C bands. Based on a derived analytical model, the relative change in maximum integrated gain at the respective perturbation frequency was observed and compared with lossless TDFAs. At an estimated small-signal attenuation of 0.36 (corresponding to small-signal attenuation coefficient α = 0.01 / m), a frequency shift of 1.44 THz with a reduction in integrated gain of 45 dB was obtained for an input signal power of 250 mW. For the same set of parameters, the effect of nonlinear and loss factor was calculated and compared with present day state-of-the-art erbium-doped fiber amplifiers. The analysis helped in the selection of optimum values for small-signal gain coefficient (g0 = 0.21 / m) and TDFA length (L = 100 m) to maximize the integrated gain of the perturbations for different input signal powers. The special case pertaining to nonideal conditions with respect to the large amplitude of input perturbations was solved numerically. Dipole relaxation time was estimated (450 fs) from the results and compared with the theoretically calculated value (318 fs) for TDFAs. The results obtained can be used constructively in the selection of optimum parameters and perturbation frequency value for the design of TDFA lasers in which MI acts as an active saturable absorber.
In this paper, a grating assisted MDM-PDM hybrid (de)multiplexer based on the silicon-on-insulator (SOI) platform has been proposed and analyzed using coupled mode theory with effective index method (EIM). The proposed device consists of a multimode wide waveguide and five single mode narrow waveguides. The quasi- TE/TM modes of the wide waveguide are phase matched with the respective contra-propagating fundamental quasi-TE/TM modes of the single mode narrow waveguides. The phase matching conditions are satisfied by using different period gratings, which are surface corrugated on the wide waveguide. The proposed device structure exhibits good crosstalk, insertion loss, and return loss values.
This paper analyzes a germanium-doped silicon traveling wave Mach-Zehnder modulator (TWMZM) for high speed operation at 1550 nm wavelength. Single arm drive modulator performance using non-return-to-zero on-off keying (NRZ-OOK) driving scheme has been investigated. The phase-loss characteristics of the graded-index silicon-germanium PN phase shifter have been determined numerically. The traveling wave electrode has been designed for 1.5 mm long phase shifter. The 3 dB modulation bandwidth of the designed TWMZM is calculated to be 31 GHz at -2 V and an error-free operation of 59 Gbps has been obtained for 2 V peak-to-peak drive voltage with an extinction of ~6 dB.
The search for new doping material in S and near-C band communication window could prove as a boon for data traffic to which Thulium fits the slot optimally. The paper presents the performance estimation of Thulium doped fiber amplifiers (TDFAs) through ion-ion interaction mechanism (IM) effects consisting of homogeneous up-conversion (HUC) and pair induced quenching (PIQ) processes, also called clustering effect. Typically, the IM effects were studied as detrimental effect on signal gain, but in this work it was shown that they can also act as aiding mechanisms for early population inversion and lasing conditions at relatively lower pump power. Design parameters of TDFA were studied by carrying out the computational simulations on MatLab and OptiSystem 16 based on the mathematical model. The obtained results infers about the constructive nature of the IM effects. The optimum performance estimation parameters TDFA length was determined as 100 m with dopant area of 1μm. Due to the interplay of IM effect the optimum pump power was determined as 450 mW and signal gain of 20.32 dB instead of 650 mW when no IM effect was considered. The signal wavelength for minimum noise figure was calculated as 1460 nm. The work presented may be considered as a step closer to S and near-C band fiber optic communication systems.
In this paper, mathematical model and simulations displaying the phenomenon of modal instability (MI) in 1050 nm pumped heavily doped Thulium (Tm3+) fiber amplifier is presented. Pulse splitting effect through MI with variation in chirp parameter and non-linear fiber length was modeled and simulated. The pulses considered were sech, Gaussian, and super-Gaussian type. Model was computationally solved on MatLab and the results were verified by incorporating similar conditions and parameters on OptiSystem 16 simulation platform. Results concludes the optimum non linear length (LNL) and the chirp parameter (C = 12) which has to be taken so as to obtain continues time domain pulse train as well as linearly spaced frequency combs. The repetition rate of 500 MHz for 4 ps pulse at 1460 nm with peak sub-pulse energy of 8 nJ was obtained and has been reported to the first time (under MI mechanism) to the authors' knowledge. Optimum TDFA length was concluded as 375 m at which MI phenomenon was triggered.
Multiple transition levels covering S and near-C bands (1460 to 1565 nm) of thulium-doped fiber amplifiers (TDFAs) allows them as potential alternative to erbium-doped fiber amplifiers (EDFAs) hence getting employed in dense wavelength division multiplexing (DWDM) in optical fiber communication. We present overmodulation gain dynamics (OGD) on TDFAs using the EDFA’s Bononi and Rusch (1998) model. The paper portrays overmodulation of digital optical communication signal, of which amplitude was modulated by low-frequency (∼100 kHz), for line-surveillance and management control of optical information in DWDM TDFA systems. Signal-to-signal and signal-to-amplified spontaneous emission (ASE) transfer functions were derived to predict the system’s performance under high input signal power conditions and its variation on input modulation indices. Difference of −10.3 dB (0.093 W) in output signal gain was observed at 1490 nm signal wavelength with ASE. Output modulation index of 15% having high pass signal characteristics as of a lead compensator was observed with the applied signal frequency sweep. Overmodulation sensitivity for various levels of input signal power demonstrates undesirable 30% increment in the output modulation index at 8 dBm and 1490 nm signal wavelength, respectively, at corner frequency.
Paper presents Opto-Mechanical intrusion sensor fence with FBGs attached to mechanical accelerometers and strain
sensors, optimized on SolidWorks 2013 for desired frequency to 35 Hz, picking up accelerations/ strains and its
deployment for perimeter security. The accelerometer structure consists of inertial mass supported by an L-shaped
modified cantilever beam having non-uniform cross section area connected to base by a thin neck element which acts as
strain concentrated centre hence an optimum zone for FBG sensors placement. Bragg wavelength shifts were obtained
on Optigrating software for the obtained strain values on mechanical assembly of fence. CFD wind analysis is performed
on the assembly to obtain the spot for accelerometer’s placement to avoid false alarms up to wind velocities of 20 m/s.
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