Three Specifications of 100G QSFP28 4WDM Optics: 4WDM-10, 4WDM-20, 4WDM-40

To satisfy the increasing demands on more-cost-effective and lower-power-consumption 100G optical networks, 100G QSFP28 4WDM optical transceivers emerge in the market. 100G 4WDM series optical module currently includes three specifications in total: 100G QSFP28 4WDM-10, 100G QSFP28 4WDM-20, 100G QSFP28 4WDM-40. Today, in this article, Gigalight will mainly introduce them for you.

Before coming into today's topic, it will be better to have a knowledge of the MSA(Multi-Source Agreement) of these three specification optical transceivers: 4WDM MSA.

What Is 4WDM MSA(Multi-Source Agreement)?

The 4WDM MSA is an industry consortium dedicated to defining optical specifications and promoting adoption of interoperable 100G (4x25G) optical transceivers for 10 km based on the CWDM4 wavelength grid, and for 20 km and 40 km based on the LAN-WDM wavelength grid, over duplex single-mode fiber (SMF). These extended reaches are important for modern datacenter interconnects and mobile backhaul applications. The 4WDM MSA participants are responding to previously unmet industry needs for longer reaches, lower costs, and lower power consumption, as compared to previously available standards, in small form factors.

Introductions to Three Specifications of 4WDM Optics

The 100G QSFP28 4WDM-10 is based on the CWDM4 wavelength grid. To some degree, the QSFP28 4WDM-10 technical specification leverages the success of the CWDM4 2 km specification that has found broad acceptance in its target datacenter market. Like 100G QSFP28 CWDM4, the 100G-4WDM-10 specification employs 4 lanes of 25Gb/s using Coarse Wavelength Division Multiplexing (CWDM) technology to transport 100G optical traffic across duplex single mode fiber (SMF). Both specifications take advantage of Forward Error Correction (FEC) on the host port, in accordance with IEEE 802.3bj KR4 RS FEC. One key advantage of CWDM is that the lasers do not need to be cooled or temperature controlled, resulting in lower power consumption and simplicity of manufacturing. 100G QSFP 4WDM-10 optical module shares these advantages and furthermore are specified to be fully interoperable with CWDM4 products. The 100GE 4WDM-10 QSFP28 specification does not restrict the form factor although high-density QSFP28 modules are expected to be dominant.

100G QSFP28 4WDM-20 and 100G QSFP28 4WDM-40 are added on the basis of the 100G 4WDM-10. They employ LAN-WDM wavelength grid on the basis of IEEE 100GBASE-LR4 and ER4, over duplex single-mode fiber (SMF). Simultaneously, they also utilize the IEEE 802.3 KR4 RS FEC used on the host interface to reduce the cost.

This specification defines 4 x 25Gbps Local Area Network Wavelength Division Multiplex (LANWDM)optical interfaces for 100Gbps optical transceivers for Ethernet applications including 100GbE. Forward Error Correction (FEC) is a link requirement in order to ensure reliable system operation. Two optical transceivers communicate over single mode fibers (SMF) of length from 2 meters to at least 20 or 40 kilometers. The transceiver electrical interface is not specified by this MSA but can have, for example, four lanes in each direction with a nominal signaling rate of 25.78125Gbps per lane.

In addition, the QSFP28 4WDM-20 specification, which is an extension of the 100G-4WDM-10 10 km specification, enables customers to increase their reach using the same kind of optical components as 100GBASE-LR4 products. Similarly, the QSFP28 4WDM-40 enables 40 km reach with lower power consumption and in a smaller form factor than existing 100GBASE-ER4 compliant products that utilize a power-hungry SOA (Semiconductor Optical Amplifier).

For above-mentioned three specifications, Gigalight currently has these two: 100G QSFP 4WDM-20 and 100G QSFP 4WDM-40 optical transceiver, but the QSFP28 4WDM 40km optical transceiver module(shown as the pic) is the main one for promotion at Gigalight. For more information is at Gigalight official website.

About Gigalight:

Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

Why to Use DWDM System in MAN and What Are Its Networking Schemes?

On account that DWDM (Dense Wavelength Division Multiplexing) technology can make full use of the huge bandwidth resources of optical fiber, greatly increasing the transmission capacity of the system and reducing the transmission cost, the technology has been widely used in the large-capacity transmission of long distance network and backbone network. If DWDM technology is introduced into the metropolitan area network and access network, the whole network will become a whole of seamless connection, providing support and connection for all different services. Therefore, the DWDM system in the metropolitan area network has great superiority and development potential, which will become the inevitable evolution of the whole communication network to the all-optical network.

Why to Use DWDM System in the Metropolitan Area Network(MAN)?

In the past, the SDH (Synchronous Digital Hierarchy)/SONET(Synchronous Optical Network) is the core component of the metropolitan area network. However, this technology is with limitations. For example, it is highly structured, simplex in interface and limited on bandwidth; simultaneously, it also can not meet the diverse needs of enterprises; in addition, its cost is relatively high in the installation and operation of Ethernet by SDH/SONET technology.

DWDM technology is an alternative solution of SDH/SONET technology. It is with flexibility and wide application. The DWDM system can carry SDH, PDH, and other unrestricted digital signals or analog signals. Therefore, vendors and enterprises can use DWDM technology to provide a variety of services. The metropolitan area network based on DWDM technology can make full use of the huge bandwidth resources of optical fiber, greatly improving the transmission capacity of the system and reducing the transmission cost.

Factors to be Considered for the Application of DWDM in the MAN

The application of DWDM technology in metropolitan area network is mainly determined by 3 factors: market demand, technology development and operation cost. Market demand is the fundamental reason for the entry of DWDM technology into the metropolitan area network; the tech factor is the effective guarantee for DWDM technology to enter the metropolitan area network. The cost of DWDM is also an important consideration factor for operators to adopt DWDM. Analyzing the particularity of the metropolitan area network and improving the DWDM system to reduce the price, it is the key of the DWDM technology to gradually penetrate into the metropolitan area network&access network from the backbone network, and finally to realize the all-optical-network.

Networking Scheme of DWDM in the MAN

MAN is generally divided into metropolitan core network and metropolitan access network. Metropolitan core network mainly takes 2.5Gb/s SDH as the integrated transmission platform, which will be gradually evolved in the DWDM integrated transmission platform. According to different development stages and different application fields, DWDM mainly has three application solutions. The three basic solutions match with different superstructure schemes, which can constitute various metropolitan core schemes to adapt to application conditions and development requirements of different operators.

1. DWDM Optical Multiplexing Scheme

DWDM as the multiplexing tech is introduced into metropolitan core network, only taking optical wavelength as the virtual optic fiber to solve the tense situation of optic fiber. Currently, DWDM MAN device enters into the market basically in this method. Because of the lack of path selection, monitoring and survivability processing in the WDM optical layer, the scheme still takes SDH as the integrated transmission network platform.

2. DWDM Configurable Halo Scheme

With the continuous introduction of the DWDM optical multiplexing system in the metropolitan core network and the practicability of the configurable OADM, DWDM configurable halo scheme of the metropolitan core network can be formed by combining configurable OADM system with DWDM system. This scheme greatly enhances the function of the WDM optical layer. OADM can be configured selectively up/down/direct connection with the optical wavelength so as to achieve fast protection switching and configuration. The DWDM configurable halo scheme enables DWDM to replace SDH as a multi-services platform. It also supports various protocols and services through a single and public metropolitan core integrated transmission platform based on DWDM, and it is with these advantages such as forward compatibility (such as SDH over WDM), reducing costs (by simplifying the network hierarchy structure, reducing equipment and improving transmission efficiency), simplifying network management and improving the flexibility of network configuration.

3. DWDM Mesh Network Scheme

After the OXC with wavelength switching/routing function is put into practical application, OXC can be introduced to constitute a more complex mesh network structure on the basis of DWDM configurable halo. OXC or wavelength router is very flexible. Common OXC nodes can contain the up/down optical paths and protection function of OADM in the chain/ring structures, and can reconfigure OXC to gradually develop toward multi-rings or pure mesh network structure without interrupting the services.

Conclusion

DWDM has been widely applied in the long-haul trunk line. In MAN, due to high cost of devices, immature tech, poor compatibility of devices, etc, DWDM is still hard to be widely applied in the MAN. But with the further development of market and the advancement of tech, new MAN devices with low cost will be developed for application on account that DWDM tech is with economic efficiency in capacity expansion, good extensibility, transparency in bite rate and protocol, and also is able to provide improved service quality. Therefore, DWDM tech is with a bright prospect in the MAN.

Article Source: Gigalight official website(gigalight.com)

About Gigalight:Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

QSFP28 CWDM4 vs. QSFP28 PSM4: Which One Is Better?

Although a series of 200G or even 400G optical transceiver products emerge in the optical communication market, and they have not yet been put into commecial use currently due to that they are still in the stage of preparation in some aspects. Thus, 100G optical transceiver modules, especially QSFP28 PSM4 and QSFP28 CWDM4, are still spoiled in various application fields. Well, for these two optical transceivers, what are their differences and which one is better? The answers will be found in this article.

A Brief Introduction to QSFP28 PSM4 Optical Transceiver

PSM4, the abbreviation of Parallel Single Mode 4-channels, a optics with parallel technology, defined by the 100G PSM4 MSA(Multi-Source Agreement). It uses four lanes of parallel single fiber to deliever serialized data at a rate of 25Gbps per lane. 100GE PSM4 QSFP28 will be the optical transceiver that enables single-mode fiber to become popular in next-generation data centers due to its low cost and high configurability. It doesn’t need a MUX/DEMUX for each laser but it does need a directly modulated DFB laser (DML) or an external modulator for each fiber. QSFP28 100G PSM4 uses eight fibers, in which four fibers are for transmitting and four fibers are for receiving. A PSM4 QSFP28 optical module supports link lengths of up to 500 meters over single-mode fiber with 12 fiber MTP/MPO connectors. The light source of QSFP 100G PSM4 optic module is a single uncooled distributed feedback (DFB) laser operating at 1310nm.

A Brief Introduction to QSFP28 CWDM4 Optical Transceiver

The QSFP28 100G CWDM4 optical transceiver is a full duplex, photonic-integrated optical transceiver module that provides a high-speed link with a maximum transmission distance of 2km for 100G Ethernet. 100G QSFP CWDM4 is designed for optical communication applications compliant with the QSFP MSA, CWDM4 MSA and portions of IEEE P802.3bm standard. CWDM4 interfaces with LC duplex connectors. It converts 4 input channels of 25Gb/s electrical data to 4 channels of CWDM optical signals and then multiplexes them into a single channel for 100Gb/s optical transmission. Specifically speaking, four lanes with center wavelengths of 1270nm, 1290nm, 1310nm and 1330nm are controlled on the transmitting end. On the receiving end, four lanes of optical data streams are optically de-multiplexed by an integrated optical demultiplexer. With an optical multiplexer and de-multiplexer, one just uses a duplex single-mode fiber to connect two 100G CWDM4 optical transceivers.

QSFP28 CWDM4 vs. QSFP28 PSM4: Which One Is More Cost-Effective?

After knowing the basic information of PSM4 QSFP28 and CWDM4 QSFP28 optical transceiver, the comparison between them will be made in the following content to know which one is better. It is mainly made from perspectives of similarities and differences, shown as below:

Similarities of QSFP28 CWDM4 and QSFP28 PSM4 Optical Transceiver:

Optic Fiber Types: Both 100G QSFP CWDM4 and 100G QSFP PSM4 use single-mode fiber to transmit.

The Number of Lane: Both of 100G QSFP28 CWDM4 and 100GE PSM4 QSFP28 use 4 lanes(4×25Gbps) to achieve 100Gbps.

Wavelength: The wavelength of QSFP28 100G CWDM4 and QSFP28 100G PSM4 is around 1310 nm.

Differences of QSFP28 CWDM4 and QSFP28 PSM4 Optical Transceiver :

Connector Types: QSFP-100G-CWDM4-S optical transceiver is with LC duplex connector, while QSFP-100G-PSM4-S optics is with MTP/MPO connector.

Transmission Distance: The transmission distance of 100G QSFP CWDM4 optics is longer than that of QSFP 100G PSM4 optics. The maximum transmission distance of CWDM4 QSFP28 and PSM4 QSFP28 are respectively 2kms and 500ms.

Cost: QSFP28 CWDM4 optical transceiver module is more expensive than QSFP28 PSM4 optical transceiver module. It is on accoun that CWDM4 QSFP28 optics needs 4-wavelengths coarse wavelength division multiplexer(high in cost) while PSM4 QSFP28 optics does not need.

The Number of Optic Fiber: QSFP28 CWDM4 uses 2 single-mode fibers to transmit while QSFP28 PSM4 uses 8 single-mode fibers for transmission.

qsfp28 psm4 vs. qsfp28 cwdm4

As the components such as multiplexer/demultiplexer for the CWDM4 QSFP28 optical transceiver are very expensive, the cost of 100G QSFP28 CWDM4 optical module is much higher than that of 100G QSFP28 PSM4 optical module. It is seen from above information that QSFP28 PSM4 seemingly is more cost-effective choice than QSFP28 CWDM4. However, if the cost is taken into account from perspective of whole 100G connection, it should actually depend on the link distance. For PSM4 QSFP28 optics, as the connection distance increases, its total cost climbs up very fast due to increasing in the number of optic fibers. Therefore, 100GE PSM4 QSFP28 optics is a recommended solution with cost effectiveness for the deployment of 100G network with short reach. On the contrary, if it is to deploy 100G network with long-reach, 100GE CWDM4 QSFP28 is the better choice.

Conclusion

It is believed that the answers about what the differences between 100G QSFP28 CWDM4 and 100G QSFP28 PSM4 optical module are and which one is better are very clear. If you want to know more about them in this aspect, Gigalight official website is available for you.

About Gigalight:

Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

About QSFP28 PSM4 Optics: Do You Know These?

Although there have been 200G/400G optical transceiver products appearing in the optical communication market, and it does not mean that the era of 100G optical transceiver module has come to end. Actually, there still are various 100G QSFP28 optical module in great favour, such as 100G QSFP28 PSM4 and 100G QSFP28 CWDM4 optical transceiver, which meet users’ requirements for transmission distance and costs well. Then today let’s talk about the QSFP28 PSM4 optical transceiver in this post(QSFP28 CWDM4 optics has been talked about in the last post).

What Is 100G QSFP28 PSM4 Optical Transceiver?

PSM4, the abbreviation of Parallel Single Mode 4-channels, a optics with parallel technology, defined by the 100G PSM4 MSA(Multi-Source Agreement). It uses four lanes of parallel single fiber to deliever serialized data at a rate of 25Gbps per lane. 100GE PSM4 QSFP28 will be the optical transceiver that enables single-mode fiber to become popular in next-generation data centers due to its low cost and high configurability. It doesn’t need a MUX/DEMUX for each laser but it does need a directly modulated DFB laser (DML) or an external modulator for each fiber. QSFP28 100G PSM4 uses eight fibers, in which four fibers are for transmitting and four fibers are for receiving. A PSM4 QSFP28 optical module supports link lengths of up to 500 meters over single-mode fiber with 12 fiber MTP/MPO connectors. The light source of QSFP 100G PSM4 optic module is a single uncooled distributed feedback (DFB) laser operating at 1310nm.  

Why Is 100G QSFP28 PSM4 Optical Transceiver In Demand?

It is known that the most basic 100G interfaces currently used are 100GBASE-SR4 and 100GBASE-LR4 which are defined by IEEE. However, there exists a problem between them that reaches are either too short for practical application in data center or too long and costly. In fact, for data center operators, a 100G QSFP28 optical transceiver that is with max reach of 2km or min reach of 500m is better. Thus, MSA (Multi-Source Agreement) brings a mid-reach solution to the market. And 100G QSFP28 modules with PSM4 interface are the products in this revolution. They are much less expensive than the 10km 100GBASE-LR4 modules, and support longer distance than 100GBASE-SR4 QSFP28 optical modules.

What Are the Advantages of QSFP28 PSM4 Optical Transceiver?

In addition to the common merits of QSFP28 transceiver module, such as high bandwidth, low insertion loss, high data rate and so on, the most prominent advantage of QSFP-100G-PSM4-S is shown in its cost. It is known that CWDM4 QSFP28 optical transceiver needs an optical multiplexer/de-multiplexer, operating around 1310nm with CWDM technology. After that, the amount of the components leads to the high cost of CWDM4 modules. While 100G QSFP28 PSM4 optics, unlike 100G QSFP28 CWDM4, need these components. Thus, by comparison, CWDM4 is more expensive than PSM4. As for the other types, QSFP28 100G SR4 or QSFP28 100G LR4, both are known to be high in cost.

Factors to Be Considered for the Deployment of QSFP28 PSM4 Optical Transceiver

Compared with 100GBASE-LR4, the cost of 100GE PSM4 QSFP28 optical transceiver module is much lower. But QSFP28 PSM4 needs to connect with eight parallel single-mode optic fiber for use, while 100GBASE-LR4 optical transceiver just needs 2 single-mode optic fibers. After that, if the optical fiber link is too long, QSFP 100G PSM4 optical transceiver module will have less advantages in the deployment cost. Therefore, when deploying PSM4 QSFP28, these two aspects need to be considered: parallel single-mode optic fiber has been deployed in data center; the transmission distance of optical fiber link is within 500m.

Summary

All in all, 100GE PSM4 QSFP28 optics provides a cost-effective solution for the users who demands mid-reach transmission at low cost. Above all is about the contents Gigalight wants to share with you. If you want to know more about it, welcomr to visit Gigalight official website(www.gigalight.com).

About Gigalight:

Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

Essential Things You Should Know about CWDM

With the emerging of CWDM(Coarse Wavelength Division Multiplex) tech in the optical communication indusrty, various CWDM optical transciever products appear in the markets, such as CWDM SFP+, CWDM SFP, CWDM XFP, 100G QSFP28 CWDM4 and so on. Well, today, Gigalight will have an introduction to CWDM from these viewpoints that you should have a control of it.

CWDM Definition and CWDM System Principle

1. The Definition of CWDM

CWDM(Coarse Wavelength Division Multiplex), is a low-cost WDM transmission technology for MAN（Metropolitan Area Network) access layer. Speaking in principle, CWDM uses the optical multiplexer to multiplx the optical signals with different wavelengths onto the single fiber for transmission. On the receiving end of the link, the mixed signals on the optical fiber are demultiplexed into signals with different wavelengths via optical demultiplexer, and are connected to the corresponding receiving devices.

2. The Principle of CWDM System

On account that the wavelength interval of CWDM system is wide, the requirement for technology index of laser is low. Besides, due to that the wavelength interval reach 20nm, the maximum wavelength shift of the system can reach 6.5℃ to +6.5 ℃; the emission wavelength accuracy of laser can be extended to ±3nm; in the range of working temperature (－5℃～70℃), the wavelength shift caused by temperature change is still within the allowable range,the laser is not required to control the system without temperature. After that, the structure of laser is greatly simplified and the yield rate is increased.

In addition, the larger wavelength spacing means that the structure of the multiplexer/demultiplexer is greatly simplified. For example, the coating layer number of the filter in CWDM system can be reduced to about 50 layers, while that of 100GHz filter in the DWDM system is about 150 layers, which leads to higher yield rate and lower cost. The cost of CWDM filter is less over 50% of than that of DWDM filter, and will be further reduced with the increase of automatic production technology and batch size.

Advantages and Features of CWDM Tech

1. Taking Full Advantage of the Low-Loss Waveband of Optic Fiber

Making full use of the low-loss waveband of optic fiber and increasing the transmission capacity of optical fiber, the physical limit of transmitting information by one fiber can be doubled or be added by several times. Currently, a fraction of low-loss spectrum (1310nm-1550nm) of optical fiber is applied. The wavelength division multiplexing(WDM) can make full use of the huge bandwidth(25THz)of the single-mode fiber, and the transmission bandwidth is sufficient.

2. Able to Transmit Multiple Signals On the Same Optical Fiber

With the ability to transmit 2 or several non-synchronous signals on the same fiber, it is beneficial for digital signals and analog signals, independent of the data rate and modulation mode. Simulatneously, can be flexibly removed out of or added to the channels in the middle of line.

3. With High Flexibility

For the established optic fiber system, especially for early-laid optical cable with few fibers, as long as the original system is with redundant power rate, the capacity can be expanded, multiple unidirectional signals or bidirectional able to be transmitted without great changes to the original system. It is with high flexibility.

4. Quick and Convenient to Restore

Due to the reduction to application of optic fiber to a large extent, the cost is greatly decresed. Besides, because it is less in the number of optic fiber, it is quick and convenient to restore when failure appears.

5. Reducing the Cost

The shareability of active optical devices reduces the cost of transmitting multiple signals or adding new services.

6. Improving the Reliability of the System

The active equipment in the system has been greatly reduced, so that the reliability of system is improved. Currently, because multichannel carrier optical wavelength division multiplexing (WDM) has high requirements for optical transmitter and optical receiver,it is difficult to implement in tech. Simultaneously, the application of optical cables with multifibers does not bring about the critical shortage of transmission businesses of traditional broadcast TV. Therefore, the WDM is not widely applied. However, with the development of the CATV integrated services, the increasing demand for network bandwidth,the implmentation of various selective services, the consideration on cost for the network upgrade, etc, the features and advantages of WDM are gradually emerging in the CATV transmission system, showing a broad application prospect and even affecting the development pattern of the CATV network.

Applications of CWDM

1. Network Expansion and Upgrading: able to convert any input optical wavelength into fixed ITU-CWDM output optical wavelength, simultaneously to transmit up to dozen channels of optical signals, which greatly expands the transmission capacity and utilization of optical fiber, saves the time and cost of laying optical fiber cables, and starts new businesses without affecting the original businesses.

2. Hybrid Transmission of Various Signals: suitable for the upgrading of SDH, ATM, Ethernet, Fiber Channel devices, long distance line relay, analog signal transmission, and hybrid transmission of digital and analog signals in one fiber, within 10Mb/s to 2.5 Gb/s rate.

3. Mode Conversion: able to convert the single-mode optical wave into any single-mode/multi-mode optical wave, which is suitable for various complex network conditions.

4. Wavelength Conversion: able to convert any wavelength of single-mode/multi-mode optical wave into CWDM wavelength, or to convert CWDM wavelength into another arbitrary wavelength, the transmission distance able to reach several hundreds of kilometers.

5. Optical Relay: multiple CWDM can be connected in series to increase transmission distance (up to several hundred kilometers).

6. Security Networking: multiple separate virtual optical networks on the physical channels can be constituded on a pair of optical fibers, to protect the network from attacks of all software viruses and hackers. Its security is far higher than that of the general VPN, especially suitble in the fields of government, public security and banking, etc.

Conclusion

Above all is an overview of coarse wavelength division multiplex. Apart from meeting the requirements for cost saving, it is also with high reliability and flexibility, which are also key factors in the application of optical transceiver products and in the process of data transmission. For CWDM products, except for CWDM SFP+, CWDM SFP, CWDM XFP optical transceiver module, the mainly-recommended one of Gigalight is QSFP28 CWDM4 optical transceiver at present.(more details are at gigalight.com).

About Gigalight:
Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

Things You Should Know about Dispersion

For optical transceiver, dispersion also is the factor not to be ignored. Maybe many people are unfamilair with this term, and have little kowlege of what impacts it has on optical transceiver module. Then Gigalight will have an introduction to it in this article from these comprehensive perspectives.

What Is the Dispersion?

Dispersion is a kind of physical phenomenon. The reason why it forms is that the different group velocity under different frequency/mode of transmision signal of optic fiber causes the distortion of transmission signals. In optical transceivers, the dispersion of optical modules will limit the transmission distance. Let's learn from the following aspects.

The Reasons Why Dispersion Appears

On account that the speed of electromagnetic wave with different wavelength is different in the same media, optical signal with different wavelength reach the receiving end in the different time due to the accumulation of transmission distance. After that, the pulse to be widened and then the signal values can not be distinguished.

Types of Dispersion

The dispersion of optic fiber is mainly composed of modal dispersion, material dispersion and waveguide dispersion. Thereinto, the material dispersion and waveguide dispersion are related to wavelength, so they are collectively referred to as wavelength dispersion.

1. Modal Dispersion: among the multimode optic fibers, there are various modes of transmission. For the different modes, the path of transmission is different so that the time of reaching the end is also different, which causes the strentchment of the pulse. This is the modal dispersion.

2. Material Dispersion: material dispersion is caused by the characteristics of optic fiber materials, and each material has different values for different transmission wavelengths.

3. Waveguide Dispersion: after taking the optical pulse from light source with certain spectrum into the optical fiber, the time of arrival at the end is also different because the optical transmission paths of different wavelengths are not same. Then the pulse is broadened. This kind of dispersion is caused by the optical waveguide of the optical fiber. Therefore it is also called the waveguide dispersion.

The Impacts of Dispersion on Optical Transceiver

The damage of system performance related to fiber dispersion can be caused by many factors, which mainly include intersymbol interference, mode partition noise and so on.

1. Intersymbol Interference:

the dispersion of optical fibers will lead to the broadening of the transmitted light pulse. The actually received waveform is combined with many line spectrum of the laser in the optical module. Even if the receiver can perfectly balance the waveform of the single line spectrum, but it will be disconnected because the same waveform generated by the line spectrum is with different disperison. After that, the combined waveform is different from that of single line spectrum, and it will still cause the non-ideal balance.

2. Mode Partition Noise:

It is one kind of sytem damage caused by the combination of the dispersion effect with the spectral characteristics of the laser in optical module. Although the sum of the power of each spectral line in the laser is definite, and the power of each spectral line is fluctuant. When the spectral lines of the laser pass through the optic fiber, the receiving waveforms with different bits are different on account that the original dispersion of optic fiber makes the delay of spectral lines different, forming the broadening of the receiving pulse.

Above all is about the introduction to dispersion. Hoping it can be beneficial to those who get involved in it for the first time and want to have a knowledge of it. More information is at Gigalight official website(gigalight.com).

About Gigalight:

Gigalight is a design innovator in global optical interconnect field. A series of optical interconnect products include: optical transceivers, passive optical components, active optical cables, GIGAC MTP/MPO cabling, cloud programmers & checkers, etc. Three applications are mainly covered: Data Center & Cloud Computing, MAN & Broadcast Video, and Mobile Network & 5G Optical Transmission. Gigalight takes advantage of its exclusive design to provide clients with one-stop optical network devices and cost-effective products.

Do You Really Know SDI(Serial Digital Interface) in These Aspects?

Maybe most of people have a knowledge of SDI(Serial Digital Interface), but when it really comes into it, how many people are there indeed familiar with it? Then today, Gigalight will make a comprehensive introduction to you about it in these aspects.

What is SDI?

SDI (Serial Digital Interface) is a digital video interface standard made by SMPTE organization. This serial interface transmits every bit of data word and corresponding data through single channel. Due to the high data rate of serial digital signal (a kind of digital baseband signal), it must be processed before transmission.

What Are the Main Types of SDI Video Optical Transceiver?

SDI video SFP optical transceiver can be divided into various types according to different factors. For example, according to operating wavelength, they can be classified into 1310nm, 1490nm, 1550nm and CWDM wavelengths video SFP transceivers; according to operating rate, they can usually be divided into 3G-SDI, 6G-SDI and 12G-SDI video SFP transceiver.

What Are the SDI Digital Video Matrix and Its Main Functions?

The digital video matrix refers to that the m channel video signal is transmitted into the electronic device on the n channel monitoring device via array convention. In addition, it is also available to achieve the video switching via the digital cross-point chip, and to achieve the channel shift mainly by the manual mode to plug copper shaft connector of the wiring frame before the digital video matrix appears. At present, the digital matrix is distinguished in the work bandwidth. For example, for the device that can support 3G-SDI high-speed signal, the automatic balancing function can usually be achieved in both input and output terminal of each channel; the high-end device is with CDR clock regeneration function; the form of interface is with BNC copper shaft interface; it also supports the optic fiber interface of video SFP slot, also adopts the modular design, and flexible in the configuration. After that, it is more convenient for users to use.

What Is the Difference Between HDMI and SDI Optical Transceiver?

Different in the Transmission Mode: HDMI is with the parallel transmission mode, the quantity of cables reaches up to 19 pairs; while SDI is with serial transmission mode, the quantity of cables is one pair.

Distinguished in Applications: HDMI is for application of consumption products, such as consumption-grade camera, game box, high-definition TV, and other digital video output; while SDI is for broadcast market, is applied in the TV station and studio, and so on. HDMI interface supports HDCP encryption to protect HD digital copyright, while SDI does not support it.

What Does the Speed Rate of SDI Include?

Standards	Types	Speed Rate
SMPTE 259M	SD-SDI	270Mbit/s, 360Mbit/s, 143Mbit/s, 177Mbit/s
SMPTE 344M	ED-SDI	540Mbit/s
SMPTE 292M	HD-SDI	1.485Gbit/s, 1.485/1.001Gbit/s
SMPTE 372M	Dual link HD-SDI	2.970Gbit/s, 2.970/1.001Gbit/s
SMPTE 424M	3G-SDI	2.970Gbit/s, 2.970/1.001Gbit/s
SMPTE ST-2081	6G-SDI	6 Gbit/s
SMPTE ST-2082	12G-SDI	12 Gbit/s

Conclusion

Above is a comprehensive introduction to SDI. Hoping this post can help you have a better knowledge of it so that it will be beneficial to the applications of related products. If you want to know more information about it or others, Gigalight official website(gigalight.com) is a good choice for you.