Simplified ROADM module and its applications in transmission networks


The simplified ROADM can be applied in the transmission networks to improve the equipments utilization factor, partly solving the problems of the peak time communications block (jam) among nodes. It also provides a way to realize the dynamic traffic re-arrangement between the rings.

Features

• Low cost
• good scalability
• low interferes with existing signals in the inherit networks

Other Information

• The TLFF ROADM solution and sub-band add/drop filters
  
  
  
  The mechanism how TLFF(Tunable laser+ fixed filter) work is shown above picture. The source node signals emitted are firstly captured by the fixed filter at the destination node; In other word, the fix wavelength is the destination "address code". After download the wavelength, the tunable laser in the destination node aims the fixed wavelengths of the source node and sends out return signal back to the networks. So that a double ways connection is set up.Another way is FLTF(Fixed laser +Tunable filter), which has the similar principle as the TLFF.
  
  
• Applications of simplify ROADM module in the transmission networks
  
  
  
  1) In the prevalent equipments of MAN (Metropolitan area networks) or LAN (local area networks) now, what dominated is the SDH ring or the MSTP equipment based on the SDH ring. A simple update is to change of the old equipments to the new equipments, and the new equipments in each node are formed to be a new SDH ring. But it is not economical to replace network equipment frequently. The case of the traffic jam mostly takes place during the peak time. A major guideline of the customs satisfaction improvement is the ability to provide enough bandwidth during the peak time;
  2) With the help of the simplified ROADM module above mentioned, a reconfigured optical internet can be set up by the use of the original equipments which are replaced during network reconstruction. So the communication bandwidths during the peak period are geminately increased. For example, among the four nodes shown right, the equipments in each original node of 2.5Gbit/s can be used to directly connect with any of the other nodes during the peak time when the equipments update from 2.5Gbit/s to 10Gbit/s.
  3) In order to decrease insertion loss of the TLFF module further; and maintains the stabilization of the communication traffic on the original "fixed runway"; and decrease the possibility of their working condition influenced, in addtion to the the TLFF module shown above, a pair of the sub-band add/drop filter is extra added when it is inserted into the original ring. By the use of the simplified ROADM solution and sub-band add/drop filter mentioned above, the fixed SDH host rings and the reconfigured ROADM rings can completely share one fiber that will simplify the control and the maintenance of the network.
  
  
• ROADM solution for dynamic services interchange between two rings
  
  
  
  The reconfigurable inter-connected optical network is constructed by the use of the sub-band add/drop filter mentioned above, and can be used to agilely interchange the traffics among the rings. The method how to get through two rings is introduced as above picture. The cross-connected module of sub-band is consisted of two pairs of add/drop filter and a 2x2 optical switch. When the 2x2 optical switch of the cross-connected module between two rings is open, the two rings are respectively independent, and the four wavelengths in the same sub-band work for the corresponding dynamic reconfigured interconnection of each ring respectively. When the optical switch of the module is crossed closed, the two rings become a large ring for the sub-band, each node respectively located in the two rings can be directly connected with the help of the cross inter-connected module.