From Next Generation SONET/SDH

3.2.3   Timing Aspects

In modern networks, the bit rate has exceeded by far the gigabit per second rate and,
therefore, the performance of timing circuitry must meet stringent specifications.
Timing affects the bit error rate (BER) and signal performance, and circuits are
characterized by an accuracy that is defined in parts per million (ppm) pulses, by jitter,
and by wander. If a path consists of several nodes or stations, each having its
own timing circuitry, then the timing effects may be compounded over the path. Because
of the importance of this issue, standards agencies have issued recommendations
pertaining to the accuracy of timing characteristics and their measuring methods.

ITU-T has issued recommendations on performance, timing, and measurements
(G.823, G.828, O.150, O.151). Per GR-253-CORE specification, jitter is defined as
the “short-term variation” of a signal’s significant instants from their ideal position
in time. “Short-term variation” implies some frequency oscillation greater than or
equal to a frequency demarcation. In the North American hierarchy (DS1–DS3) the
demarcation between jitter and wander is 10 Hz. Jitter network element (NE) criteria
(see GR-499-CORE for details) are specified as:

  • Jitter Transfer (per interface category)—defined as the jitter transfer characteristics
    (limits) of an NE.
  • Jitter Tolerance (per interface category)—defined as the point-to-point amplitude
    of sinusoidal jitter applied on the OC-N (SONET/SDH) input signal
    that causes a 1-dB power penalty.
  • Jitter Generation (per interface category)—defines the limits of jitter generated
    by an NE without jitter or wander at its inputs. In communications systems,
    payload mapping, bit stuffing, and pointer adjustments are sources of


Products & Services
Fiber Optic Couplers
Fiber optic couplers are optical devices that connect three or more fiber ends, dividing one input between two or more outputs, or combining two or more inputs into one output.
Network Cards and Network Controllers
Network cards and network controllers are expansion boards inserted into computers that allow them to connect to a network.
Network Modems
Network modems (modulators-demodulators) are devices or programs that allow computers to transmit data over telephone lines. They convert digital computer data to analog sound waves and then demodulate the carrier signals to decode the transmitted information.
Fiber Optic Receivers
Fiber optic receivers are instruments that convert light into electrical signals. They contain a photodiode semiconductor, signal conditioning circuitry, and an amplifier.
Wireless Network Components
Wireless network components are used to build or replace worn out devices within a wireless network.

Topics of Interest

3.3   REVIEW OF DATA NEWORKS The Local Area Network (LAN) is a standardized (IEEE 802.3 series) nonhierarchical, low-cost multiple-access network. Switching is accomplished by store and forward...

High speed, high-performance timing applications often require a combination of XO/VCXOs, clock generators, clock buffers and jitter cleaning clocks to satisfy system timing requirements. Each...

7.1   INTRODUCTION As data is transmitted over a medium, attenuation, combined noise, and jitter sources all distort the shape of the transmitted bits, both in amplitude and time, to such a...

Dr. TOM CRAWFORD, GEOFF THOW, and PETER SCOTT Hewlett-Packard Ltd. 6.1 INTRODUCTION The error-rate performance of digital transmission links is frequently degraded by the following factors: Additive...

This chapter discusses system requirements for a PLL. Noise basics, phase noise, time-domain response, acquisition, jitter, and spurious signals are the system requirements that are studied in detail.