Transport
Detailed Information
How do we define transport:
- Photonische Netze
- DWDM Systemtechnik
- CWDM Systemtechnik
- SDH Technik
The demands for a backbone are to be differentiated according to the carrier’s requirements.
A service provider (SP) with the aim to offer high bandwidth to carriers or other SP’s has to rely on the more economical DWDM system technologies. Later on, his existing network can be extended by pure optical components and in such a way developed to a photonic network.
The carrier who offers various services to his end customer lays more value on a wide and dynamic service portfolio and on Quality of Service (QoS).
Nowadays, necessary transmission capacities in the backbone are mainly realized with SDH technology. The further increase of transmission capacity can be economically covered by the use of DWDM systems.
As a network structure in DWDM networks, a ring structure with Optical Add Drop Multiplexer (OADM) comes along with priority. This enables as well as in the case of SDH - transport networks the automatic backup-route switching. The OADM provides the access to single wavelengths in the network structure. The cross-connecting of the wavelengths, if necessary, in case of a further network expansion leads to the Optical Cross Connects (OXC) und with it to the purely photonic network.
Regarding the procedure of the wavelengths multiplexing, various wavelengths are to be assigned to the transferring data signals and transmitted in a glass fiber through optical multiplexing.
Principle view of a photonic layer
Every wavelength corresponds to one channel with a transmission rate up to 10 Gbit/s.
The data within defined wavelength bands are to be transferred and lie mainly at 1550 nm +/- 20 nm and with it in the optical window, also named Cband.
According to the number of channels on the glass fiber the outcome of this is an overall capacity of n times 10 Gbit/s. For this reason, a multiple usage of the glass fiber will be achieved.
The channel distance amounts to 200 GHz, to 100 GHz, to 50 GHz or to 25 GHz and corresponds with it to 1.6 nm, to 0.8 nm, to 0.4 nm or to 0.2 nm.
DWDM systems are to be distinguished according to the operating area.
In the campus area distances of 2 to 5 kms will be reached.
The Short-Haul-Area or Metro-Area stands for middle distances and the Long-Haul-Area describes the use of DWDM from 100 kms in Europe.
The named areas are tuned to the country-typical circumstances. Some manufacturers have already developed pure optical components in order to realise cross connect functions. These functions make the entrance in the photonic network levels possible and therefore an electric transformation for the cross connecting is unnecessary.
Comparision of TDM-based transmission vs. DWDM-transmission