Transmission – Backbone – Core
We make markets in secondary market equipment for ATM, PDH, SDH, SONET, DWDM and CDWM technologies from multiple manufacturers. Additionally we deal in all of the peripheral components like digital cross connects, DSX Panels, Jack Fields, Echo Cancelers, Network and line interfaces, Transcoders and Channel Banks.
ATM at the networking system provides predictable, guaranteed quality of service. From end to end, every component in an ATM network provides a high level of control. The QoS feature of ATM also supports time dependent (or isochronous) traffic. Traffic management at the hardware level ensures that quality service exists end-to-end. ATM supports integration of voice, video, and data services on a single network.
The PDH design allows the streaming of data without having isochronous to synchronize the signal exchanges. PDH clocks are running very close, but not exactly in time with one another so that when multiplexing, signal arrival times may differ as the transmission rates are directly linked to the clock-rate. PDH allows each stream of a multiplexed signal to be bit stuffed to compensate for the timing differences so that the original data stream could be reconstituted exactly as it was sent.
Synchronous digital hierarchy (SDH) is an international technology standard that utilizes light-emitting diodes (LED) or lasers for synchronous optical fiber communication. SDH was developed to eliminate synchronization issues and replace the plesiochronous digital hierarchy (PDH) system for bulk telephone and data exchange.
Synchronous optical networking (SONET) is a standardized digital communication protocol that is used to transmit a large volume of data over relatively long distances using a fiber optic medium. With SONET, multiple digital data streams are transferred at the same time over optical fiber using LEDs and laser beams.
Dense wavelength division multiplexing (DWDM) is wavelength division multiplexing (WDM) with typical channel spacing of 100 GHz for 40 channels and 50 GHz for 80 channels. Each channel contains a TDM (time division multiplex) signal. And each of up to 80 channels can carry 2.5 Gbps for a total of 200 billion bits per second by the optical fiber. These signals use the 3rd transmission window, called the C-Band, meaning the light beam wavelengths are between 1530nm to 1565nm. (nm = a nanometers or a billionth of a meter).
Coarse wavelength division multiplexing (CWDM) is a method of combining multiple signals on laser beams at various wavelengths for transmission along fiber optic cables, such that the number of channels is fewer than in dense wavelength division multiplexing (DWDM) but more than in standard wavelength division multiplexing (WDM).
CWDM systems have channels at wavelengths spaced 20 nanometers (nm) apart, compared with 0.4 nm spacing for DWDM. This allows the use of low-cost, uncooled lasers for CWDM. In a typical CWDM system, laser emissions occur on eight channels at eight defined wavelengths: 1610 nm, 1590 nm, 1570 nm, 1550 nm, 1530 nm, 1510 nm, 1490 nm, and 1470 nm. But up to 18 different channels are allowed, with wavelengths ranging down to 1270 nm. Because of the use of lasers with lower precision, a CWDM system is less expensive and consumes less power than a DWDM system. However, the maximum realizable distance between nodes is smaller with CWDM.