1.9 Summary
27
1.4 Consider two sine wave signals that have the same frequency. Suppose that
the second signal is offset by one quarter of a cycle with respect to the first
wave. What is the phase shift in degrees between the two signals?
1.5 A common digital binary waveform is represented by a sequence of two types
of pulses called bits. As Fig. 1.14 shows, the time slot in which a bit occurs is
called the bit interval or bit period. The presence of a pulse in a time slot is a
one bit or 1 bit, whereas the absence of a pulse represents a zero bit. The bit
intervals are regularly spaced and occur every 1/R seconds or at a rate of R bits
per second. Depending on the signal coding method, a bit can fill the entire
bit period (Fig. 1.14a) or only part of it (Fig. 1.14b). The number of photons
N in a digital pulse can be found from the relation
N =
(Pulse width)(Pulse power)
(Energy/photon in eV)(1.6 × 10 −19 J/eV)
Consider a 1 ns pulse with a 100 nW amplitude at various wavelengths. How
many photons are in such a pulse at each of the following wavelength: 850,
1310, 1490, and 1550 nm?
1.6 What is the duration of a bit for each of the following three signals which
have bit rates of 64 kb/s, 5 Mb/s, and 10 Gb/s?
1.7 Convert the following absolute power gains to decibel power gains: 10
−3 , 0.3,
1, 4, 10, 100, 500, 2
n .
Fig. 1.14 A common digital binary waveform is represented by a sequence of two types of bit
pulses
27
1.4 Consider two sine wave signals that have the same frequency. Suppose that
the second signal is offset by one quarter of a cycle with respect to the first
wave. What is the phase shift in degrees between the two signals?
1.5 A common digital binary waveform is represented by a sequence of two types
of pulses called bits. As Fig. 1.14 shows, the time slot in which a bit occurs is
called the bit interval or bit period. The presence of a pulse in a time slot is a
one bit or 1 bit, whereas the absence of a pulse represents a zero bit. The bit
intervals are regularly spaced and occur every 1/R seconds or at a rate of R bits
per second. Depending on the signal coding method, a bit can fill the entire
bit period (Fig. 1.14a) or only part of it (Fig. 1.14b). The number of photons
N in a digital pulse can be found from the relation
N =
(Pulse width)(Pulse power)
(Energy/photon in eV)(1.6 × 10 −19 J/eV)
Consider a 1 ns pulse with a 100 nW amplitude at various wavelengths. How
many photons are in such a pulse at each of the following wavelength: 850,
1310, 1490, and 1550 nm?
1.6 What is the duration of a bit for each of the following three signals which
have bit rates of 64 kb/s, 5 Mb/s, and 10 Gb/s?
1.7 Convert the following absolute power gains to decibel power gains: 10
−3 , 0.3,
1, 4, 10, 100, 500, 2
n .
Fig. 1.14 A common digital binary waveform is represented by a sequence of two types of bit
pulses