Q. The minimum pulse energy needed to maintain a given bit-error-rate (BER) which any practical receiver must satisfy is known as ___________

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Q. A digital optical fiber communication system requires a maximum bit-error-rate of 10⁻⁹. Find the average number of photons detected in a time period for a given BER.

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Q. For a given optical fiber communication system, P(e) = 10⁻⁹, Zₘ = 20.7, f = 2.9×10¹⁴, η = 1. Find the minimum pulse energy or quantum limit.

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Q. An analog optical fiber system operating at wavelength 1 μm has a post-detection bandwidth of 5MHz. Assuming an ideal detector and incident power of 198 nW, calculate the SNR (f = 2.99×101¹⁴ Hz).

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Q. The incident optical power required to achieve a desirable SNR is 168.2 nW. What is the value of incident power in dBm?

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Q. In the equation given below, what does τ stands for?

Zₘ = ηP₀τ/hf

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Q. Which are the two main sources of noise in photodiodes without internal gain?

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Q. The dominating effect of thermal noise over the shot noise in photodiodes without internal gain can be observed in wideband systems operating in the range of ________

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Q. A silicon p-i-n photodiode incorporated in an optical receiver has following parameters:

Quantum efficiency = 70%
Wavelength = 0.8 μm
Dark current = 3 nA
Load resistance = 4 kΩ
Incident optical power = 150 nW.
Bandwidth = 5 MHz

Compute the photocurrent in the device.

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Q. In a silicon p-i-n photodiode, if load resistance is 4 kΩ, temperature is 293 K, bandwidth is 4 MHz, find the thermal noise in the load resistor.

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Q. ________________ is a combination of shunt capacitances and resistances.

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Q. ______________ is used in the specification of optical detectors.

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Q. A photodiode has a capacitance of 6 pF. Calculate the maximum load resistance which allows an 8MHz post detection bandwidth.

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Q. The internal gain mechanism in an APD is directly related to SNR. State whether the given statement is true or false.

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Q. ____________ is dependent upon the detector material, the shape of the electric field profile within the device.

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Q. For silicon APDs, the value of excess noise factor is between _________

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Q. __________ determines a higher transmission rate related to the gain of the APD device.

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Q. _________________ APDs are recognized for their high gain-bandwidth products.

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Q. APDs do not operate at signal wavelengths between 1.3 and 1.6 μm.

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Q. How many circuits are present in an equivalent circuit for the digital optical fiber receiver?

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