Introduction: Global communications are advancing by leaps and bounds, the role of communication networks is becoming more and more important, and the construction of communication networks needs to be continuously expanded. At present, DWDM (Dense Wavelength Division Multiplexing) and OTN (Optical Transport Network) technologies are widely used in network communication construction. DWDM technology greatly improves the transmission capacity of optical fiber networks, but it is insufficient in optical domain signal processing and service scheduling. Can not meet the high standards of broadband data services. As an evolution of DWDM technology, OTN has a variety of customer signal encapsulation and transparent transmission, large-particle bandwidth multiplexing, flexible cross-connection and configuration scheduling, powerful overhead and maintenance management capabilities, and enhanced networking and protection capabilities, etc., OTN The unique advantages of the device have gradually replaced DWDM equipment. The following briefly discusses the comparison of DWDM and OTN transmission technologies.

1. The conceptual difference between DWDM and OTN

DWDM: Dense Wavelength Division Multiplexing (DWDM) is a combination of multiple optical waves in a range of optical wavelengths and a single optical fiber in the vicinity of a window with a wavelength of 1550 nm. Laser technology for increasing bandwidth on fiber-optic backbones. More specifically, the technique is to multiplex the tight spectral spacing of individual fiber carriers in a given fiber to take advantage of the achievable transmission performance (eg, to achieve minimal dispersion or attenuation). Thus, with a given information transmission capacity, the total number of fibers required can be reduced.

OTN (Optical Transport Network) is a transmission network that organizes networks in the optical layer based on wavelength division multiplexing technology and is the next generation backbone transmission network. The OTN switching module is added in the technology, so that the system can flexibly dispatch communication services, so that the client information can be expanded, promoted, increased, and the network communication service capability is improved, thereby solving the traditional WDM network without wavelength/sub-wavelength. Poor service scheduling capabilities, weak networking capabilities, and weak protection capabilities.

2. Different signal formats

DWDM technology does not have a corresponding frame structure. During operation, the wavelength of a single signal is converted into a corresponding wavelength in network communication through a converter, and the transmission wavelength is multiplexed by optical technology.

OTN has a complete frame mechanism. It can realize the electrical cross function similar to SDH by scheduling the wavelength by electric crossover technology, so that the signals of small particles can be combined and transmitted in a large channel. The channel of OTN also has a large size like SDH. Small and small containers, OTN has the ability to access and process from the system, improving bandwidth utilization efficiency. OTN technology can also supervise the working performance and faults of network communication and electrical regeneration. In the process of performance fault detection, OTN technology is superior.

3. Differences in networking and protection mechanisms

The DWDM technology networking mode is mainly point-to-point, chain, star, and ring network. Only the base layer protection is provided in the protection mode. The protection mode is mainly optical multiplex section protection, and 1+1 and 1 are adopted on the optical path. : 1 protection. The terminal device is not protected. This protection mode requires two optical cables that are independently routed. The self-healing protection of the DWDM service is performed in the SDH ring network.

The OTN networking is usually a ring network or a mesh network. It can provide line 1+1 protection, wavelength 1+1 protection, customer side 1+1 protection, ODUk protection, optical layer and electrical layer protection

4. Business scheduling capabilities

In OTN, data configuration can be used for cross-connection (similar to SDH service configuration), which can access multiple types of services at the same time, and can realize intelligent scheduling of services. Can provide optical layer wavelength level, electrical layer sub-wavelength level service hybrid scheduling capability, optical layer scheduling capability: optical layer provides OADM wavelength scheduling mode, can pre-plan input/output fixed wavelength, can also use AWG input

All wavelengths are input/output, and the wavelength of the upper and lower services needs to be connected to the service card. Electrical layer scheduling capability: Provides distributed electrical crossover of ODU0/ODU1/ODU2/ODU2e/ODU3/ODU4 particles, and the adjacent slot cross capacity reaches 100/200Gbps.

5. Application scenario

DWDM is mainly used in the provincial trunk network and the provincial backbone network. The main method is point-to-point networking, which can realize the line protection. If the line protection mode is adopted, more lines need to be laid and the cost is high. Therefore, the self-healing protection of the DWDM service is combined with the SDH ring network and is widely used.

The OTN network has improved the ideal solution for the large-bandwidth granular service. The OTN network is deployed in the inter-provincial backbone network, the provincial backbone network, and the metro core layer of the telecom operators, and the scheduling of service particles above Gb/s is provided. The provincial backbone network carries long-distance services such as PSTN/2G/3G/4G/internet. The OTN network can implement multiple forms of protection and has strong protection capabilities. The backbone network in the province carries services such as the NGW/3G/4G/IPTV large customer line between the backbone routers. The metro core network carries the large-granular service between the local network core router and the aggregation router, and builds the provincial backbone network OTN. And the metropolitan area network core layer OTN network.

6.Sharetop DWDM and OTN advantages

The Sharetop 4U active wavelength division system can greatly increase the network capacity and make full use of fiber resources. The single-wavelength transmission rate is 1.25Gbit/s to 100Gbit/s, and the number of service channels is up to 96 waves. Various networking modes can be configured. The Sharetop 4U active wavelength division system consists of wavelength converter module, mux module, de-mux module, demultiplexer, optical amplifier, dispersion compensator, network management unit and other components to complete the transmission and shaping transmission of network signals. Received to form a stable DWDM transmission system. It has the characteristics of flexible networking, good capacity expansion, security and stability, and diverse management modes. The Sharetop 4U active wavelength division system has rich practical experience in the fields of backbone network, city telecom operators, national power grid, military private network, security monitoring, and college education network.

The Sharetop OTN2800 series is a new generation of wavelength division products for the optical transmission market. Smooth upgrade: support multi-chassis cascading and smooth expansion and upgrade capabilities, support 10Gbit/s service upgrade 100/200G bit/s service, support 40 wave/80 wave smooth upgrade capability, single fiber maximum transmission capacity can be 8T/16T. Networking mode: OTN2800 can be flexibly configured as OTM (Optical Multiplexing Terminal), OLA (Optical Line Amplification), REG (Electrical Trunking), OADM (Optical Add/Drop Multiplexer) and other device types, supporting point-to-point and chain Networking methods such as ring and mesh.

Advantages of the OTN2800 series

(1) Provide hybrid scheduling capability for optical layer wavelength level and electrical layer sub-wavelength level services.

(2) It can realize ultra-long span and ultra-long-distance transmission capability, support multi-level cascade function of electric relay regeneration, and relay regenerative transmission distance can reach tens of thousands of kilometers.

(3) The OTN2800's 100G/200G board provides wavelength adjustment and wavelength adjustment through a tunable wavelength module, all of which can be adjusted in the 96-wave range of the C-band 50 GHz interval. The wavelength adjustable machine technology avoids the traditional wavelength division fixed wavelength conversion mode, which can greatly facilitate the opening of the service and realize the flexible distribution of the wavelength.

(4) Supporting 10G, 100G, and 200G signals The mixed OTN2800 supports the hybrid transmission of the current mainstream rate 10G signals and 100G signals on the same platform, and provides a mature mixed transmission networking solution. Users can therefore flexibly network to achieve a smooth transition from 10G systems to 100G systems. In the design of the hybrid transmission scheme, in addition to fully considering the common problems of two rate signal transmission distances and path spacing, the channel interference problem between different modulation formats is also considered comprehensively to ensure the transmission performance of the system.

7. OTN trend

In terms of informationization and business bandwidth, OTN is a derivative of DWDM. OTN technology inherits and combines the advantages of SDH and WDM, and expands the networking function that is compatible with service transmission requirements. There are significant improvements in network applications, scheduling capabilities, service access capabilities, and network management monitoring capabilities to meet new service quality requirements. OTN system service transmission transparency, superior error correction capability, flexible optical and optoelectronic layer scheduling capabilities, with the advent of the 5G era, the application of OTN technology will be more popular in the market, which is an inevitable trend of future network development.