OCF: Q9

Frage	Antworten
Discuss the relations of SNR, EVM, Q and RIN.	If we assume data aided reception we have that: Image: 9 1 (binary/octet-stream)
How are the SNR and the OSNR defined?	Image: 9 2 (binary/octet-stream)
How is the SNR related to the Shannon limit?	Image: 9 3 (binary/octet-stream)
Name the different processing steps which need to be done in an optical digital coherent receiver.	1. Chromatic Dispersion Compensation 2. Deskew & Orthonormalization 3. Timing Recovery 4. Polarization Division De-Multiplexing 5. Carrier and Phase Recovery 6. Equalizing 7. Demapping
How can chromatic dispersion be compensated and what is the characteristic of the compensation filter?	A dispersion compensating fiber (DCF) is one example of a filter which can undo chromatic dispersion. The inverse filter is defined as: Image: 9 5 (binary/octet-stream)
Describe the impairments which should be mitigated by de-skewing and orthonormalization.	- Timing might be of because of different optical path lengths in the Rx after the splitting into Ix, Qx, Iy, Qy. - The 90° coherent Rx could have an offset from the ideal 90°.
What are the origins of timing errors?	Tx and Rx have different clocks which aren't synchronized. Rx typically samples at a slightly higher rate to prohibit data loss (aliasing).
Name different timing recovery algorithms and explain the basic ideas.	-Early-Late Gate: 3 samples. If s0=s2 then s1 is at ideal position -Mueller Müller: weight s[n] and s[n-1] with the expectation and use their difference to estimate the correction. -Square: Square the signal and look at the spectrum. Peeks should indicate Fourier coefficients from which the the timing can be estimated.
Which effect should be equalized by polarization division de-multiplexing? How can this effect be mathematically described?	Rotation, Phase-Retardation: estimate: theta and phi for PDM Image: 9 9 (binary/octet-stream)
Describe the different techniques which are used for polarization division de-multiplexing. How do their cost functions look like?	Image: 9 10 (binary/octet-stream)

Discuss the relations of SNR, EVM, Q and RIN.

If we assume data aided reception we have that:

How are the SNR and the OSNR defined?

How is the SNR related to the Shannon limit?

Name the different processing steps which need to be done in an optical digital coherent receiver.

1. Chromatic Dispersion Compensation 2. Deskew & Orthonormalization 3. Timing Recovery 4. Polarization Division De-Multiplexing 5. Carrier and Phase Recovery 6. Equalizing 7. Demapping

How can chromatic dispersion be compensated and what is the characteristic of the compensation filter?

A dispersion compensating fiber (DCF) is one example of a filter which can undo chromatic dispersion. The inverse filter is defined as:

Image: 9 5 (binary/octet-stream)

Describe the impairments which should be mitigated by de-skewing and orthonormalization.

- Timing might be of because of different optical path lengths in the Rx after the splitting into Ix, Qx, Iy, Qy. - The 90° coherent Rx could have an offset from the ideal 90°.

What are the origins of timing errors?

Tx and Rx have different clocks which aren't synchronized. Rx typically samples at a slightly higher rate to prohibit data loss (aliasing).

Name different timing recovery algorithms and explain the basic ideas.

-Early-Late Gate: 3 samples. If s0=s2 then s1 is at ideal position -Mueller Müller: weight s[n] and s[n-1] with the expectation and use their difference to estimate the correction. -Square: Square the signal and look at the spectrum. Peeks should indicate Fourier coefficients from which the the timing can be estimated.

Which effect should be equalized by polarization division de-multiplexing? How can this effect be mathematically described?

Rotation, Phase-Retardation: estimate: theta and phi for PDM

Image: 9 9 (binary/octet-stream)

Describe the different techniques which are used for polarization division de-multiplexing. How do their cost functions look like?

Image: 9 10 (binary/octet-stream)

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