Performance metrics • The Bit Error Rate (BER): • The primary measure of performance of a digital system • The probability that an error will be made in the detection of a received bit – BER < 10-9, for telecommunications – BER < 10-12, for data transmission
• Measured by counting the number of errors occurring during transmission over a long period of time: – BER = (# bit errors)/(total # of bits transmitted)
Aussois, 26 November 1998
Digital optical communications
2
Performance metrics The Bit Error Rate (BER): – BER = Perr (Probability of Error)
Perr = P ( 0 | 1 ) P (1 ) + P (1 | 0 ) P ( 0 ) 2 e − SNR 1 e − SNR 1 1 P ( 0 | 1) = , P (1 | 0 ) = 2 π SNR 1 2 π SNR D − V0 V − D SNR 1 = 1 , SNR 0 = σ1 σ0
2 0
0
– BER is a strong function of SNRi: • BER(SNR = 6) = 10-9 • BER(SNR = 7.9) = 10-15
PDF Optimum decision level
2 σ0 2 σ1
P(0|1)
V0 Aussois, 26 November 1998
P(1|0) D
V1
Digital optical communications
3
Performance metrics
– – – – –
Jitter Noise Inter-Symbol Interference (ISI) Patterning effects Bit errors
Amplitude Noise & ISI
"1"
Jitter
Eye opening
The Eye-Diagram: • It is the overlay of all possible states of a sequence • Powerful diagnostic:
"0" Time Decision level
Aussois, 26 November 1998
Digital optical communications
Optimum sampilng instant
4
Performance metrics Bit Rate-Distance Product: • To compare different systems a figure of merit is necessary • The product: (Bit Rate) û (Distance), is a measure of the information carrying capacity of a link • “Distance”: – is the maximum distance that can be achieved without the use of repeaters between the transmitter and the receiver
• Optimize a link capacity À increase B û L
Aussois, 26 November 1998
Digital optical communications
5
Transmission Impairments Attenuation & Noise: • As a signal travels along a fiber (or cable) it is attenuated: P
•
PT ⋅ 1 0
A ⋅L 1 0
Due to receiver noise, a minimum power has to be detected by the receiver in order to achieve the desired BER The maximum distance over which a signal can travel before it is to week to be detected is: P 10 L m ax = lo g T A PR Signal Power (dB)
•
(L ) =
−
Launch power Splices
Receiver overload
Margin
Receiver sensitivity Distance (km)
Aussois, 26 November 1998
Digital optical communications
6
Transmission Impairments fiber attenuation • Attenuation in optical fibers is caused by: – Rayleigh scattering: dominant at the “shorter” wavelengths (1600nm) – Both phenomena combine to produce a low-loss “window” with absolute loss minimum at 1550nm – Absorption peak caused by OH ions (~1400nm)
Aussois, 26 November 1998
Digital optical communications
7
Transmission Impairments ISI, Dispersion and Bandwidth • In a physical link, the available bandwidth is limited • As the symbol rate approaches the bandwidth limit the received pulses become broadened versions of the transmitted pulses • For moderate to sever bandwidth limitations the received pulses start to overlap • This overlap is called Intersymbol Interference (ISI) • Bandwidth limitations and fiber dispersion are the common causes of ISI • Large amounts of ISI can not be simply corrected by increasing the received signal power
ISI no "0" level "1"
"0"
"1"
"1"
"1"
"1"
Limited BW Channel Transmitted pulses
Aussois, 26 November 1998
t
Received pulses
Digital optical communications
t
8
Transmission Impairments Bandwidth: • Electronic circuits have finite bandwidths • Bandwidth limitations can be equalized • Equalization increases the receiver high frequency noise – This increases the BER – The BER can be restored by increasing the received signal power – The increase in power necessary to restore the BER is called the Power Penalty
Preamp
SNI(ω)
Aussois, 26 November 1998
Hp(ω)
HE(ω)
ω
ω
Equalizer
Output
Hp(ω) HE(ω)
ω
Digital optical communications
SNO(ω)
ω
ω
9
Transmission Impairments Dispersion: • As signal pulses travel along a fiber they spread and start to overlap • Dispersion effects result in: reduction of the high frequency response of the system • Small amounts of dispersion can be corrected by equalization • Equalization has an associated power penalty • Systems operate typically with dispersion penalties less than 1dB • To maintain the dispersion penalty less than 1dB the RMS pulse spread has to be less than one-quarter of T: σt < T/4 h(t)
h(t)
δ(t) Fibre
t
Aussois, 26 November 1998
2 σt
H(ω) = H(0) [1 - 0.5 ω2 σt2]
Digital optical communications
t
10
Transmission Impairments Dispersion: • Since, σt increases with fiber length • And, a power penalty less that 1 dB requires σt
Tx. Detector channel. LHC clock (40MHz). Gain. 82 728 chan n e ls (barrel +. 2 en d caps). Radiation hard environment. CMS Electromagnetic Calorimeter.
The CMOS inverter. ⢠Technology. ⢠Scaling. ⢠Gates ..... For acceptable phase margin. Place the zero 1/Ï .... Add VCO phase noise. Update the VCO period ...
D. A. Johns and K. Martin, âAnalog Integrated Circuit Design,â John Wiley & Sons 1997, ISBN 0- ... B. Razavi, âA Study of Phase Noise in CMOS Oscillators,â IEEE Journal on Solid-State ... http://www.ife.ee.ethz.ch/~ichsc/ichsc_chapter11.pdf.
Design of Analog Integrated Circuits and Systems by Kenneth R. ... Design of Analog CMOS Integrated Circuits ... CMOS Circuit Design, Layout, and Simulation.
Clock skew control and frequency multiplication. Ext. CLK. Clock pad. PLL ...... Algorithm: ⢠Slice the time in very thin intervals (much smaller than T vco. ).
The silicon area of large memory cells is dominated by the size of the memory core, it is thus crucial to keep the size of the basic storage cell as small as possible.
An active low pass filter. ⢠A charge-pump and a capacitor .... Can we run the starved inverter infinitely slow?. ⢠... Signal and the Inverted signal available.
that of a DLL you notice some similarities but as well some very fundamental differences: .... 3rd always buffer the VCO signal to make the transfer ..... âMonolithic Phase-Locked Loops and Clock Recovery Circuits Theory and Design,â ..... In one
... pattern to the wafer surface. â Process the wafer to physically pattern each layer of the IC ... (photo resist: light-sensitive organic polymer). ⢠The photoresist is exposed to ultra violet light: ... active by an rf-generated plasma anisotr
NRZI non-return to zero invert on ones. â Manchester and Bi-Phase Mark. â 3B/4B, 5B/6B and 8B/10B, done in groups of bits before serialization. BiPhase Mark.
CMOS power budget: â Dynamic power consumption: ⢠Charging and discharging of capacitors. â Short circuit currents: ⢠Short circuit path between power rails ...
... CMS tracker analogue data link. â The CMS tracker data path. â The linear laser-driver ... Monitoring. Serial/Parallel. Local. Address. Control & Data. Interface.
Dec 17, 2004 - M.J.M. Pelgrom et al., âA 25-Ms/s 8-bit CMOS A/D Converter for Embedded Applicationâ, ... components can be attributed to two classes of effects. .... Technical Digest of the IEEE International Electron Device Meeting 1997, pp ...
May 20, 2007 - Below an excerpt form correspondence with Hans Camenzind: ..... This means that any spectral content of the phase noise that is above 10 ...
in the vernier scale (lower) lines up with a tick mark in the reference scale (upper). [36]. 38 ..... Almasi, L. et al., New TDC electronics for a PesTOF tower â in NA49, ... Mota, M., A high-resolution Time-to-Digital Converter â users manual, C
Dec 17, 2004 - The definition of âMoore's Lawâ has come to refer to almost anything related to ..... The following data are taken from the design manuals of different CMOS technologies. N. D. Arora et al., "Modeling the Polysilicon Depletion Effe
Since then he has worked in communications system design, software design, ..... This book is not intended as a text on optical communication. It is a very high level ..... a beam of light shines on an interface between glass and air. This is ......
