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Questions and Answers
What causes the difference in color observed between the 1 km and 1 m long multimode optical fiber outputs?
In the context of optical fibers, why does light towards the blue region experience greater scattering out of the fiber?
How does the decibel scale simplify loss calculations in optical fibers?
What would be the total loss in decibels for a 60 km fiber link with a loss of 0.6 dB km-1 and 5 connectors, each with a loss of 2.5 dB?
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Why is power amplification important in fiber optics?
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If a laser beam power decreases from 7 mW to 21 mW after traversing through an optical fiber, what is the total loss in decibels?
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What is the formula for measuring the power level of a beam in dBm?
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In the context of optical fibers, what does 'Ns' represent in the equation for power received at the detector?
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How can the total loss of a fiber link be calculated based on the information in Example 27.5?
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What is the relation between dBm and mW, according to the text?
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What does 'a' represent in the formula provided in Eq.(8)?
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If the input power is 3.2 dBm and a loss of 0.8 dB occurs, what is the output power in dBm?
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What is the total loss in the optical communication system as described in Example 27.7?
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If the laser power at the detector is -29.74 dBm, and the detector can detect down to -40 dBm, what is the excess power margin at the detector?
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What is the maximum allowable loss in the system if the input power is 1 mW (0 dBm) and the maximum loss is approximately 38 dB?
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If the fiber loss coefficient is 0.5 dB km-1, what is the maximum distance the system can have without splice and connector losses?
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What does Pmin represent in the context of pulse detection in an optical communication system?
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What does Np represent in the context of pulse detection in an optical communication system?
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Study Notes
Color Difference in Multimode Optical Fibers
- The difference in color observed between the 1 km and 1 m long multimode optical fiber outputs is due to the varying degrees of scattering of different wavelengths of light.
- Light towards the blue region experiences greater scattering out of the fiber because of its shorter wavelength.
Decibel Scale in Optical Fibers
- The decibel scale simplifies loss calculations in optical fibers by allowing for the addition of individual losses in decibels rather than multiplying fractions.
- The total loss in decibels for a 60 km fiber link with a loss of 0.6 dB km-1 and 5 connectors, each with a loss of 2.5 dB, would be 41 dB (36 dB from the fiber length and 5 dB from the connectors).
Power Amplification in Fiber Optics
- Power amplification is important in fiber optics to compensate for signal losses during transmission, ensuring that the signal remains strong enough to be detected accurately.
Power Loss Calculations
- If a laser beam power decreases from 7 mW to 21 μW after traversing through an optical fiber, the total loss in decibels is 11.5 dB.
- The formula for measuring the power level of a beam in dBm is P(dBm) = 10 * log10(P(mW) / 1 mW).
Power Received at the Detector
- In the equation for power received at the detector, 'Ns' represents the number of photons required for detection.
Total Loss Calculation
- The total loss of a fiber link can be calculated by adding the individual losses in decibels from the fiber length, connectors, and splices.
dBm and mW Relation
- dBm is related to mW by the formula P(dBm) = 10 * log10(P(mW) / 1 mW).
Formula Variables
- In the formula provided in Eq.(8), 'a' represents the attenuation coefficient of the fiber.
Output Power Calculation
- If the input power is 3.2 dBm and a loss of 0.8 dB occurs, the output power in dBm is 2.4 dBm.
Optical Communication System Loss
- The total loss in the optical communication system as described in Example 27.7 is 38.2 dB.
Excess Power Margin
- If the laser power at the detector is -29.74 dBm, and the detector can detect down to -40 dBm, the excess power margin at the detector is 10.26 dB.
Maximum Allowable Loss
- If the input power is 1 mW (0 dBm) and the maximum loss is approximately 38 dB, the maximum allowable loss in the system is 38 dB.
Fiber Distance Limitation
- If the fiber loss coefficient is 0.5 dB km-1, the maximum distance the system can have without splice and connector losses is 76 km.
Pulse Detection in Optical Communication Systems
- Pmin represents the minimum power required for pulse detection in an optical communication system.
- Np represents the number of photons required for pulse detection in an optical communication system.
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Description
Test your knowledge on calculating fiber optic power levels using dBm scale. Understand the conversion between milliwatts and dBm, and how to apply the formula to determine power output. Practice solving power level calculations for fiber optic systems.
