Frequently asked questions about Optical networks

Many students and engineers asks this below questions

1.What is Coherent Transmission?

As mobile networks advance towards data networks, intelligent terminals are widely used, and new services, such as IPTV,eCommerce and cloud computing,online gaming are increasing rapidly, the transmission capacities of legacy networks have to be improved. The system supports high-speed transmission with the use of advanced modulation formats like ePDM-16QAM, ePDM-QPSK, ePDM-BPSK, and coherent detection technologies to meet the high-speed transmission requirements on OSNR, CD, PMD, and nonlinear effects. It offers ultra-large bandwidth (400G, 200G, 100G and 40G).

2.What is ROADM?

It’s the abbreviation of reconfigurable optical add/drop multiplexer. With ROADM technology, flexible optical-layer grooming is available. The ROADM reconfigure wavelengths by blocking or cross-connecting the wavelengths. It changes the static allocation of the resource to flexible and dynamic allocation.

The main technology of RAODM is WSS. The WSS module on a WSS board splits a colored light signal into multiple parallel monochromatic signals and adjusts the optical power of each monochromatic signal. The WSS module directs each monochromatic signal into the corresponding multiplexer using its 1xN optical switch. The WSS module then multiplexes the monochromatic signals into one signal for further transmission. In this way, a monochromatic signal can be transmitted out of the board through any port.

3.What is ASON?

It’s the abbreviation of Automatically Switched Optical Network. ASON introduces Generalized Multiprotocol Label Switching (GMPLS) control plane to achieve dynamic connection management, automatic discovery, protection & restoration, and CAPEX & OPEX reduction. The control plane of ASON complies with Link Management Protocol (LMP), Link Management Protocol (OSPF), and Resource Reservation Protocol-Traffic Engineering (RSVP-TE) protocols.

ASON can transport services of different Service Level Agreements (SLAs) based on customers’ requirements. The SLA divides services into various levels according to the service protection capability.

There two kinds of ASON, optical-layer ASON and electrical-layer ASON. The optical-layer ASON, which is also known as WSON, is based on flexible ROADM with the using of WSS technologies to implement colorless, directionless and contentionless applications. As to electrical-layer ASON, there two types of electrical-layer ASON: OTN ASON and SDH ASON. Electrical-layer ASON is based on optical-layer server trails. The OTUk link or VC link may be inconsistent with the physical topology. OTN ASON can be easily deployed on standard OTN networks to improve the network reliability.


NB:I will describe each of the above terminology in another post