wideband travelling wave semiconductor optical amplifier

[Rajguru M. Mohan]

Hi,
I want to know about application of wideband travelling wave semiconductor optical amplifier in optical communication.
Here i am uploading image of OFDM-WDM PON in which for the uplink, the wideband travelling wave semiconductor optical amplifier (WBTW-SOA) is used to simulate the traveling wave SOA that is based on an identical hidden edge SOA. A transmitter source Tx and CW laser source are coupled by using an optical coupler and the output is applied to WBTW-SOA. The output signal of WBTW-SOA will be sent via the uplink of SMF. Before reaching the PD at the receiver side, EDFA is used to amplify the signal.

Now, i Want to know why wideband travelling wave semiconductor optical amplifier is being used in this design.
What is its functions?

Please explain.

Thanks and regards,
Rajguru

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[Hamza Ali Abbas Khan]

Hi Rajguru M Mohan.
I would like to mention that A travelling-wave model of a semiconductor optical amplifier based non-linear loop mirror is developed to investigate the importance of travelling-wave effects and gain/phase dynamics in predicting device behaviour. A constant effective carrier recovery lifetime approximation is found to be reasonably accurate (±10%) within a wide range of control pulse energies. Based on this approximation, a heuristic model is developed for maximum computational efficiency. The models are applied to a particular configuration involving feedback. Travelling wave soa is an optical amplifier which causes polarization sensitive type amplification by the occurrence of a change in the carrier density of its material when a weak optical signal is injected into it. The carrier density occurs by releasing some of the energies of its electrons in the form of photons to adjust with the initial wavelength of the weak optical signal. I hope this will be of some help to you.
Thanks

[Aabid Baba]

Hello Rajguru M Mohan,
I to some extent agree with what Hamza Ali Abbas Khan has mentioned. I too feel that wideband travelling wave semiconductor optical amplifier in optical communication are being used to investigate the importance of travelling-wave effects and gain/phase dynamics in predicting device behaviour. A constant effective carrier recovery lifetime approximation is found to be reasonably accurate (±10%) within a wide range of control pulse energies.I hope this will help you to some extent.
Regards

[Rajguru M. Mohan]

Hi,
A high performance of the designed wideband travelling SOA is obtained and analyzed with the optimized values of injection current, optical confinement factor, input power and active length.
I also agree to the points of Hamza Ali Abbas Khan, I think that wideband travelling wave semiconductor optical amplifier in optical communication are being used to investigate the importance of travelling-wave effects and gain/phase dynamics in predicting device behaviour.
Traveling wave (TW) SOA, which relies on a single passgain, ideally has no mirror reflections and is the most desirable layout. This is
typically achieved by either AR coatings on the cleaved mirror facets and/or a tilted
waveguide with respect to the facets.
The effect of these reflections
on a TW amplifier is called “gain ripple.” Any design that deliberately uses this feature
to enhance the gain due to cavity resonance is called a Fabry-Perot (FP) amplifier.

Thnaks,

[Karan Ahuja]

Hi.

I want to mention that optical amplifier (SOA) technology has matured to the point where commercial devices are available for use in optical communication systems. Mathematical models are required to aid in the design of SOAs and to predict their operational characteristics. Many such models have been presented in the literature [1]–[5]. However, many of these models make assumptions that restrict the range of operating conditions over which the SOA can be modeled. These assumptions are used either to obtain analytic solutions for the amplifier characteristics, or to aid numerical computation. SOAs can be used to simultaneously amplify a number of signals at different wavelengths. To model such an application, a wideband model of the SOA is required. A comprehensive wideband model of a bulk InP–InGaAsP SOA is presented. Through the use of suitable gain models it can be extended to SOAs with quantum-well active regions. In the model, the relationship between spontaneous and stimulated emission is clarified. This relationship does not require the use of a spontaneous emission factor used in many models. Spontaneous emission within the amplifier is modeled by traveling-wave power equations, which neglect the phase of the spontaneous signal. The model can be applied to determine the steady-state properties of an SOA over a wide range of operating regimes. numerical algorithm is described which enables efficient implementation of the model. Simulations and comparisons with experiment are given which demonstrate the versatility of the model.
You may refer to
https://www.google.co.in/urlsa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwj_563wM7NAhVIoZQKHYrWCcMQFggpMAE&url=http%3A%2F%2Foptiwave.com%2Fcategory%2Foptisystem-manuals%2Foptisystem-tutorials%2Fa9-optical-system-soaamplifiers%2F&usg=AFQjCNEzCB_UFpV58WlD0no_r0MTQI_FEQ

Thanks

[Karan Ahuja]

Amplification of ultra-short optical pulses in SOA produces considerable spectral broadening and distortion due to the non-linear phenomenon of self-phase modulation. The physical mechanism behind SPM is gain saturation, which leads to intensity-dependent changes of refractive index in response to variations in carrier density. Signal-gain saturation in SOA is caused by a reduction of the population inversion in the active layer due to an increase in stimulated emission. Gain saturation characteristics are especially important in optical repeaters and multi-channel amplifiers which require high-power operation.
You may also refer to
http://www.ocrg.ul.ie/JQE01.pdf

SOA Gain Saturation – Gaussian Pulses

Thanks

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