Ch11Sec1_1

Ch11Sec1_1 - THE FIBER FORUM Fiber Optic Communications...

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Dr. Joseph C. Palais 11.1 1 THE FIBER FORUM Fiber Optic Communications Dr. JOSEPH C. PALAIS PRESENTED BY
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Dr. Joseph C. Palais 11.1 2 Chapter 11 Noise and Detection
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Dr. Joseph C. Palais 11.1 3 Noise degrades signals. Without noise, it would not matter how little optical power arrived at the receiver. Signal quality is measured in several ways. Analog systems: The signal-to-noise ratio (SNR) is the measure. Digital systems: The bit-error-rate (BER) is the measure. It this chapter we determine how to evaluate the SNR and BER.
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Dr. Joseph C. Palais 11.1 4 Section 11.1 Thermal and Shot Noise
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Dr. Joseph C. Palais 11.1 5 11.1.1 Thermal Noise Recall the simple receiver circuit: R L v P - + i V b
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Dr. Joseph C. Palais 11.1 6 Even if P = 0 (and the photodiode dark current is zero), a current i = i NT will exist in resistor R L . It has zero average value, but it is random, like: i NT t
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Dr. Joseph C. Palais 11.1 7 The current arises from the random thermal motion of the electrons. The instantaneous noise power is R L i 2 NT The average thermal noise power is R L i 2 NT R L i 2 NT R L i 2 NT t
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Dr. Joseph C. Palais
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This note was uploaded on 01/26/2011 for the course EEE 546 taught by Professor Palais during the Spring '10 term at ASU.

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Ch11Sec1_1 - THE FIBER FORUM Fiber Optic Communications...

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