Analog Link And Digital Link

Jan 15 • Cyber Security, Education • 9864 Views • 4 Comments on Analog Link And Digital Link

Analog link and Digital link

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Digital Link:-
– In the operation of a digital optical fiber link, first a light source launches a certain amount of optical power into a fiber.

– The optical signal becomes attenuated due to loss mechanisms in the fiber at connectors. 

-The optical power level at the end of a link defines the signal to noise ratio at the receiver which is used to measure the performance of both analog and digital communication systems.

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POINT TO POINT LINK:-
-It is the simplest kind of lightwave systems.

-It is used to transport information in the form of a digital bit stream from one place to
another.
-The length of the link vary from less than a kilometer to thousands of kilometer.

LINK POWER BUDGET:-

– It is used to ensure that enough power will reach the receiver to maintain reliable performance during the entire system lifetime.
– The receiver sensitivity is the minimum average power required by the receiver..
– It takes simple form in decibel units with optical powers expressed in dBm units

RISE TIME BUDGET:-

– It is used to ensure that the system is able to operate properly at the intended bit rate.
– If the bandwidth of the individual system components exceeds the bit rate then the total system may not be able to operate at that bit rate.

POWER PENALTY:-
– Some sources of power penalty are-
• Modal Noise
• Dispersive Pulse Broadening
• Mode-Partition Noise
• Frequency Chirping
• Reflection Feedback and Noise

ANALOG LINK:-

– A carrier to noise ratio analysis is used instead of a signal-to-noise ratio analysis.
– If the time-varying analog drive signal is s(t), then the output optical power P(t) is
P(t) = Pt[1 + ms(t)] Here Pt is optical power level at the bias current point, and the modulation index
is given by

m=ppeak/pt

– For a sinusoidal received signal, the carrier power C at the output of the
receiver is
C=1/2(mRMPo)2
where P0 is the average received optical power.

– The carrier-to-noise ratio then is given by

CNR=C/RIN(RPo)2Be+2qrM2FMPoBe+(4kBT/Req)BeFt
where the noise terms in the denominator are due to RIN, shot, and thermal
noises respectively.

EXPECTED QUESTIONS WITH ANSWERS

1) What Is Digital Link?

ANS:- – In the operation of a digital optical fiber link, first a light source launches a certain amount of optical power into a fiber.

– The optical signal becomes attenuated due to loss mechanisms in the fiber at connectors.

-The optical power level at the end of a link defines the signal to noise ratio at the receiver which is used to measure the performance of both analog and digital communication systems.

2) What Is Point To Point Link?

ANS:- -It is the simplest kind of lightwave systems.

-It is used to transport information in the form of a digital bit stream from one place to
another.
-The length of the link vary from less than a kilometer to thousands of kilometer.

3) What Is Link Power Budget And Rise Time Budget?

ANS:- Link Power Budget:-

– It is used to ensure that enough power will reach the receiver to maintain reliable performance during the entire system lifetime.
– The receiver sensitivity is the minimum average power required by the receiver..
– It takes simple form in decibel units with optical powers expressed in dBm units

RISE TIME BUDGET:-

– It is used to ensure that the system is able to operate properly at the intended bit rate.
– If the bandwidth of the individual system components exceeds the bit rate then the total system may not be able to operate at that bit rate.

4) What is Analog Link?

ANS:-

– A carrier to noise ratio analysis is used instead of a signal-to-noise ratio analysis.
– If the time-varying analog drive signal is s(t), then the output optical power P(t) is
P(t) = Pt[1 + ms(t)] Here Pt is optical power level at the bias current point, and the modulation index
is given by

m=ppeak/pt

– For a sinusoidal received signal, the carrier power C at the output of the
receiver is
C=1/2(mRMPo)2
where P0 is the average received optical power.

– The carrier-to-noise ratio then is given by

CNR=C/RIN(RPo)2Be+2qrM2FMPoBe+(4kBT/Req)BeFt
where the noise terms in the denominator are due to RIN, shot, and thermal
noises respectively.

GATE Syllabus-

1. Gate Syllabus for Electronics and Communication 2014

2, Gate Syllabus for Computer Science and Information Technology 2014

3, Gate Syllabus for Engineering Science 2014

IES Syllabus-

1. IES Syllabus For Electronics and Telecommunication

2. IES Syllabus for General Ability

 

ANALOG LINK AND DIGITAL LINKlink power budgetrelated questions and answersrise time budget

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