Optical Communications

Simulation 1: Fiber

Pham Quang Thai – pqthai.hcmut@gmail.com

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Basic

Components

Double click to set component’s parameters

Double click to set layout’s parameters

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Problem 1: signal degradation over fiber

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• Layer’s parameters: – Sequence length: 8 bits, bit rate: 5 Gbps

• Laser’s parameters: – Wavelength: 1310 nm and 1550 nm

• Fiber’s parameter: – Length: 10 km – Dispersion and attenuation: use SMF-28-100 specs

(maximum values).

• Observe the signal in time domain at the fiber’s output. In which case the signal is more distorted?

• Observe the signal’s power at the fiber’s output. Find the attenuation in each case.

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Problem 2: simple application

• A simple optical sensor using reflected light to estimate the sensing medium’s refractive index is shown below. Fresnel reflection between two medium (n1 and n2) is calculated using:

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1 2

1 2

n n

n n

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• Laser’s parameter: – Wavelength: 1550 nm, input power: 0 dBm

• Circulator: – Choose the correct circulator and use its specs

• Fiber: – Use SMF-28-100 specs, length: 0.5 km, turn on Rayleight, Raman and

Brillouins scattering.

• Reflector: – Calculate Fresnel reflection at the fiber end between air (n=1) and

fiber’s core (n=1.48)

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• Notices: – All components’ inputs in Optisystem need an input value. So unused

port need a dummy input (“optical null” component)

– Bi-directional components in Optisystem need several simulation loops to calculate. If there is bi-directional component in the layout, set the layout’s “Signals” tab as follow.

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• Run the simulation. What is the received reflected optical power? (remember in increase “Signal index”)

• Salt solution has the following refractive index depend on its concentration. Plot the received power and explain how the system can be use to find salt concentration in water?

Salt (g/100g) 0 10 20 26.5

Refractive index

1.333 1.3505 1.3684 1.3807

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