2.2 Types of sdh modules in the ring
Calculation of repeater section length limited by fiber attenuation is performed according to the formula:
,
where PB is power budget (PB = ptr -prec);
Apic – attenuation of the plug-type connection (0,5dB)
Apc – attenuation of the permanent connection (0,1dB)
Ares –attenuation of the permanent connection (6dB)
Calculations:
PB=9+30=39 (dB);
Lregα
=
=
78,73 (km)
Calculation of repeater section length limited by fiber dispersion:
Lregϭ
=
Where D – chromatic dispersion coefficient of the optical fiber (ps/(nm⋅km));
∆λ– laser emitting line width, nm;
B – signal bitrate corresponding to the STM level in the ring, bit/s.
=
95.6 km
The total repeater section length is equal to:
2) Calculate a cable length at the sections:
Lcablei = 1.01∙Lsecti;
Lcable1…2 = 1.01∙115 = 116.15 (km);
3) Calculate a quantity of regenerators in the SDH ring by the next equation:
=
0
For current input data we have:
Section |
1-2 |
2-3 |
3-4 |
4-5 |
5-6 |
6-7 |
7-8 |
8-1 |
Lseci |
115 |
111 |
81 |
65 |
45 |
39 |
111 |
60 |
Lcablei |
116.15 |
122.1 |
89.1 |
71.5 |
49.5 |
42.9 |
122.1 |
66 |
Nreg |
1 |
1 |
1 |
0 |
0 |
0 |
1 |
0 |
A terminal multiplexer is a software application that can be used to multiplex several virtual consoles, allowing a user to access multiple separate login sessions inside a single terminal window, or detach and reattach sessions from a terminal. It is useful for dealing with multiple programs from a command line interface, and for separating programs from the session of the Unix shell that started the program, particularly so a remote process continues running even when the user is disconnected.
Features:
A terminal multiplexer can be thought of as a text version of graphical window managers, or as a way of putting attach virtual terminals to any login session. It is a wrapper that allows multiple text programs to run at the same time, and provides features that allow the user to use the programs within a single interface productively.
Persistence
Similar to VNC, a terminal multiplexer allows the user to start applications from one computer, and then reconnect from a different computer and continue using the same application without having to restart it. This makes accessing the same session between different locations like work and home simple. Terminal multiplexers provide terminal-agnostic functionality so that users can disconnect and reconnect using different terminal types, allowing applications to continue running without being aware of the change in terminals.
Concretely, the multiplexer starts a session (with associated processes), and then either does not attach a terminal to it, or attaches a terminal but can subsequently detach it (for example if the network connection is dropped). Since the session does not end, the processes are not sent a "hangup" signal (SIGHUP) and are not terminated, so they continue running, and one can subsequently (re)attach a terminal to the session and continue interacting, or simply leave the session unattached.
Multiple windows
Multiple terminal sessions can be created, each of which usually runs a single application. The windows are numbered, and the user can use the keyboard to switch between them. Some GUI terminal emulators provide tabs or otherwise similar functionality to this. Each window has its own scroll-back buffer, so that output is captured even when the window isn't actively displayed, and that history can be saved even when migrating to another computer. Windows can be split-screened. While some text applications have this functionality built in, a terminal multiplexer allows any application to be split-screened alongside any number of other applications.
Session Sharing
Terminal multiplexers allow multiple computers to connect to the same session at once, enabling collaboration between multiple users. The same computer can also be used to make multiple simultaneous connections, providing alternative functionality to screen-splitting, particularly for computers with multiple monitors.
A digital cross-connect system (DCS or DXC) is a piece of circuit-switched network equipment, used in telecommunications networks, that allows lower-level TDM bit streams, such as DS0 bit streams, to be rearranged and interconnected among higher-level TDM signals, such as DS1 bit streams. DCS units are available that operate on both older T-carrier/E-carrier bit streams, as well as newer SONET/SDH bit streams.
DCS devices can be used for "grooming" telecommunications traffic, switching traffic from one circuit to another in the event of a network failure, supporting automated provisioning, and other applications. Having a DCS in a circuit-switched network provides important flexibility that can otherwise only be obtained at higher cost using manual "DSX" cross-connect patch panels.
It is important to realize that while DCS devices "switch" traffic, they are not packet switches—they switch circuits, not packets, and the circuit arrangements they are used to manage tend to persist over very long time spans, typically months or longer, as compared to packet switches, which can route every packet differently, and operate on micro- or millisecond time spans.
DCS units are also sometimes colloquially called "DACS" units, after a proprietary brand name of DCS units created and sold by AT&T's Western Electric division, now Alcatel-Lucent.
Modern digital access and cross-connect systems are not limited to the T-carrier system, and may accommodate high data rates such as those of SONET.
An add-drop multiplexer (ADM) is an important element of an optical fiber network. A multiplexer combines, or multiplexes, several lower-bandwidth streams of data into a single beam of light. An add-drop multiplexer also has the capability to add one or more lower-bandwidth signals to an existing high-bandwidth data stream, and at the same time can extract or drop other low-bandwidth signals, removing them from the stream and redirecting them to some other network path. This is used as a local "on-ramp" and "off-ramp" to the high-speed network.
ADMs can be used both in long-haul core networks and in shorter-distance "metro" networks, although the former are much more expensive due to the difficulty of scaling the technology to the high data rates and dense wavelength division multiplexing (DWDM) used for long-haul communications. The main optical filtering technology used in add-drop multiplexers is the Fabry–Pérot etalon.
Newer "multi-service SONET/SDH" (also known as a multi-service provisioning platform or MSPP) equipment has all the capabilities of legacy ADMs, but can also include cross-connect functionality to manage multiple fiber rings in a single chassis. These devices can replace multiple legacy ADMs and also allow connections directly from Ethernet LANs to a service provider's optical backbone. In the end of 2003, sales of multiservice ADMs exceeded those of legacy ADMs for the first time, as the change to next-generation SONET/SDH networks accelerated.
An emerging variety of ADMs that is becoming popular as the carriers continue to invest in metro optical networks are reconfigurable optical add-drop multiplexers (ROADMs).
|
|
Terminal maltiplexer |
ADM |
|
|
|
|
There are next interfaces types:
- STM-1: S-1.1 (< 20 km), L-1.1 (< 40 km), L-1.2, L-1.3 (< 80 km);
- STM-4: S-4.1 (< 20 km), L-4.1 (< 40 km), L-4.2, L-4.3 (< 80 km);
- I (< 2 km) – interstation interface.
Considering the organization scheme of the SDH ring (fig. 2.3), we should take into account the factory length to construct actual line.
It is necessary to take into account the factory length in order to decrease the number of welding. As l=12.5, the cable length between DNN-1 and DNN-2 is 116.15 km, the SMR will be situated between them.
1)
=58.07(km) – approximate position of SMR
2)
– number of factory lengths between DNN-2 and SMR;
3) 5 ∙ 12.5 = 62.5 (km) – distance between DNN-1 and SMR;
4) 116.15 – 62.5 = 53.65(km) – distance between DNN-2 and SMR.
As l=12.5, the cable length between DNN-2and DNN-3, DNN-7and SNN-8 is 122.1 km, the SMR will be situated between them.
1)
=61.05 (km) – approximate position of SMR
2)
– number of factory lengths between DNN-3 and SMR;
3) 5 ∙ 12.5 = 62.5 (km) – distance between DNN-2 and SMR;
4) 122.1 – 62.5 = 53.65(km) – distance between DNN-3 and SMR.
As l=12.5, the cable length between DNN-3and DNN-4 is 89.1 km, the SMR will be situated between them.
1)
=45.55 (km) – approximate position of SMR
2)
–
number of factory lengths between DNN-4 and SMR;
3) 4 ∙ 12.5 = 50 (km) – distance between DNN-3 and SMR;
4) 89.1 - 50 = 39.1 (km) – distance between DNN-4 and SMR.