YKSDH series products design conforms with the latest recommendation by ITU-T and telecom equipment network access regulation by Ministry of Information Industry，all accredited telecom equipment network access license issued by MII. This equipment could be applied as STM-1/STM-4/STM-16 TM, ADM, REG or mini DXC4/1.The equipment supports various network topologies and provides all kinds of protection functions with complete functions, reliable operation, simplified and flexible configuration and all kinds of tribunal interfaces as well as powerful administrative functions.
Basically three layers frame— backbone layer, convergence layer and access layer are applied to metro network. With the development of SDH technology, SDH/MSTP ring networking is applied mostly convergence layer for metro network and back convergence layer for small and medium metro network. With the evolution of technology, SDH/MSTP equipment is applied to metro access layer is an ideal option. But as small amount and large quantity for access network services with highly request to price, except for small capacity SDH ring with highly request to network security, PDH transceiver with star topology connection are mainly used in access layer network for most cities. PDH accesses are also applied to Telecom VIPs. In order to access with VIPs A.S.A.P., large quantities of PDH equipments are applied to metro transmission network edge by point-to-point networking. A series of serious issues are produced by this access method to maintenance and scalability for the whole network.
First of all, conventional PDH optical transceiver networking is simple, most of them could only be set up as simple point-to-point network, the Central Office end equipment room will be stacked large amount of PDH optical transceivers and interface convectors or optical transceivers. This makes trouble to whole network operation and maintenance therefore goes against network architecture optimization and services integrity to operators.
Second of all, as without uniform rate standard for PDH optical interfaces, back-to-back connection could only be applied to access layer PDH optical transceiver and convergence layer SDH/MSTP through such physical interface as E1.It needs large amount of cables and DDF distribution frame which not only increases corresponding equipment room area and large attachments cost but also due to the E1circuit adjustment depends on manpower method which increases probability of poor contact for electrical interfaces leads to reduce reliability greatly to whole system and finally operators benefit is interfered.
Thirdly, applying PDH optical transceiver blocks the organic connection between convergence layer and access layer on network management so that the operation maintenance cost increased and service transit complicated. It is hard to realize centralized monitoring and flexible resource allocation therefore dead zone on management formed.
Let the past be a guide, many telecom operators come to limit large scale utilization to PDH system on telecom network, part of networks are cancelled. Telecom operators come to seek for a newly technical method or solution which not only with the merit of being more cost-effective but also overcomes the shortcoming without uniform standard and difficult maintenance, poor service quality.
To evaluate network edge through YKSDH through will be developing trend for optical access market which is the theory and struggling objective for Youke Company in these years. With the help of breaking through in SDH core chip field, Guangzhou Youke Communication Equipment Co., Ltd. kicked off YKSDH metro access network solution in due form. This idea of the whole newly project lies in pushing SDH technology to network edge truly and realizing VC-12 reached to network end directly which makes end user enjoy the benefit from SDH/MSTP technology, all customer services get through in whole SDH network. The key is that the price is compatible with PDH equipment and makes it possible to utilize SDH technology in metro access network in large scale.

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