Modern modulation methods

1. CSRZ stands for:

		a)	Carrier Suppressed Return to Zero
		b)	Chirp Suppressed Return to Zero
		c)	Carrier Shift Return to Zero
		d)	Chirp Shift Return to Zero

Evaluate your answer

2. Duobinary Modulation:

		a)	is a phase modulation
		b)	is a frequency modulation
		c)	is an amplitude modulation
		d)	is a differential amplitude modulation

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3. One of the benefits of Returning to Zero in digital modulations is:

		a)	greater tolerance to random polarization
		b)	greater tolerance to the frequency chirp
		c)	immunity to single errors
		d)	immunity to chromatic dispersion

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4. In Carrier-Suppressed Return-to-Zero:

		a)	phase at the carrier frequency is altered by π, when binary O occurs
		b)	phase at the carrier frequency is altered by π at every bit, no matter if it is binary O or 1
		c)	phase at the carrier frequency is altered by π, when binary 1 occurs
		d)	phase at the carrier frequency is altered by (2 n + 1), where n is bit number

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5. A transceiver:

		a)	is a simplifier digital signal processor used to implement the modulation algorithm
		b)	can operate as in-line amplifier for a modulator
		c)	includes a transmitter and a receiver
		d)	contains an Mach-Zehnder modulator combined with a filter

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6. In Alternate Mark Inversion:

		a)	has three logical levels 0, +1 and -1
		b)	has two logical levels 0 and 1
		c)	has four logical levels 00, O1, 10, 11
		d)	has many adaptive logical levels

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7. One of the benefits of Alternate Mark Inversion is:

		a)	good synchronization of long strings of binary zeros
		b)	good synchronization of long strings of binary ones
		c)	good synchronization of long strings of binary zeros or binary ones
		d)	suppression of the carrier frequency

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8. The principle of Duobinary Modulation is, as follows:

		a)	the phase of a symbol is shifted by π, if there is odd number (1, 3, 5...) of binary zeros
		b)	the phase of a symbol is shifted by π, if there is odd number (1, 3, 5...) of binary ones
		c)	the phase of a symbol is shifted by π, if there is even number (2, 4, 6...) of binary zeros
		d)	the phase of a symbol is shifted by π, if there is even number (2, 4, 6...) of binary ones

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9. The principle of BPSK is, as follows:

		a)	a binary zero is assigned a value of phase that differs by π from a phase assigned to a binary one
		b)	every binary zero shifts the symbol's phase by π
		c)	every binary one shifts the symbol's phase by π
		d)	every binary one shifts the symbol's phase by 180°

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10. The principle of DPSK is, as follows:

		a)	a binary zero is assigned a value of phase that differs by π from a phase assigned to a binary one
		b)	every binary zero shifts the symbol's phase by π
		c)	every binary one shifts the symbol's phase by π
		d)	every binary one shifts the symbol's phase by 90°

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11. In QPSK:

		a)	there are two levels of symbol's phase
		b)	four combinations of two bits are assigned four states of a symbol's phase
		c)	there are two levels of signal's phase, each combined with two levels of amplitude
		d)	there are two frequencies, at which two levels of signal's phase are available

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12. In QPSK:

		a)	the symbol rate is two times greater than the bit rate
		b)	the symbol rate is four times greater than the bit rate
		c)	the symbol rate is two times slower than the bit rate
		d)	the symbol rate is four times slower than the bit rate

Evaluate your answer

13. PDM-QPSK

		a)	halves the amount of possible symbol states using just one polarization component
		b)	double the amount of possible symbol states using orthogonal polarization component
		c)	uses phase division multiplexing to increase the bit rate
		d)	uses polarization division multiplexing to avoid coherent detection

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14. PDM-QPSK is a format that is suitable for:

		a)	for high reach systems operating at one frequency
		b)	Passive Optical Networks using polarization maintaining fibres only
		c)	transmission systems with coarse grid
		d)	high-speed transmission systems with dense grid

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15. Coexistence of two systems using different modulations in one fibre:

		a)	requires removing a safety band that occupies many channels
		b)	does not allow channel interleaving
		c)	can cause crosstalks from amplitude modulation channels to phase modulation channels
		d)	does not allow combining systems with different bit rates per channel

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16. Cross Phase Modulation:

		a)	is also known as CPM
		b)	can originate when interleaving channels with different modulations
		c)	is an amplitude modulation
		d)	is a frequency modulation

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17. Kerr effect:

		a)	is a change in the frequency of a material in response to an applied electric field
		b)	is a change in the phase of a symbol in response to an applied electric field
		c)	is a change in the effective index of a material in response to applied force
		d)	is a change in the refractive index of a material in response to an applied electric field

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18. The width of each channel in Orthogonal Frequency Division Multiplexing is:

		a)	Δf = B/N, where B is bandwidth and N is number of subchannels
		b)	Δf = N/B, where B is bandwidth and N is number of subchannels
		c)	Δf = B*N, where B is bandwidth and N is number of subchannels
		d)	Δf = (B+1)/(N-1), where B is bandwidth and N is number of subchannels

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19. VDMT is:

		a)	Virtual Digital Multi-Tasking
		b)	Vectored Discrete Multi-Tone
		c)	Vectored Differential Multi-Tone
		d)	Vectored Digital Multi-Tone

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20. Which claim referred to VDMT is right?

		a)	It does not require synchronization of all DMT symbols
		b)	It is a modulation widely used in xDSL technology
		c)	It cannot implement QAM modulation in particular sub-channels
		d)	It uses a vector containing information about each Differential Multi-Tone symbol

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