2018-02-27

What Is Optical Communication and Its Advantages

Optical communication is a communication way with optical wave as carrier. There are two methods to increase optical bandwidth: the first is to increase the single channel transmission rate of optical fiber; the second is to increase the number of wavelengths transmitted in a single fiber (WDM). Here Gigalight is going to introduce what optical communication is and its main advantages to help you know the field better.

What Is Optical Communication?


The basic optical fiber communication system consists of data source, optical transmitter, optical channel and optical receiver. The data source includes all the signal sources, and they are the signals obtained by the source code of voice, image and data. The optical transmitter and modulator are responsible for converting the signal into an optical signal that is suitable for transmission on the optical fiber. The optical wave window include: 0.85, 1.31 and 1.55. Optical channels include the most basic optical fiber, and the relay amplifier EDFA, etc. The optical receiver receives the optical signal and extracts the information from it, then converts it into electrical signals, and finally obtains the corresponding voice, image, data and other information.



The computers and mobile phones around us send messages via electrical signals "0 and 1". Optical communication consists of a "transmitter" that converts electrical signals into optical signals, a “receiver” that converts optical signals into electrical signals, and "optical fibers" that transmit optics.

Three Main Advantages of Optical Communication


1. Long Transmission Distance, Save Energy

Suppose you want to transmit 10Gb of information in one second (10 billion signals). If you use electrical communication, you need to adjust the signal every 100 meters. In contrast, using optical communication requires an interval of more than 100 kilometers. The fewer times the signal is adjusted, the fewer machines will be used, thus saving energy.

For example, when you phone or chat online now with your foreign friends, you will feel there is no difference with the domestic conversation, without lag in sound. In an era of electrical communication, one can transmit at a short distance and transmit less information, and international communication is mainly transmitted through satellite as relay. However, with optical communication, one can transmit at a long distance and transmit more information. Therefore, by using fiber-optic cables laid on the seafloor, it is possible to communicate with overseas. Electrical waves have the same speed as optical waves. However, because the transmission path is longer by satellite, the signal arrives slower. The submarine cable is much shorter, so the signal will be faster.

2. Transmit Massive Amount of Information at One Time

Using optical communication, a large number of users can receive the required information at the same time (movies or news, etc.). In one second, electrical communication can transmit only 10Gb of information (10 billion 0 and 1 signals). In contrast, optical communication can transmit information of up to 1Tb (1 trillion 0 and 1 signals).

3. Fast Communication Speed

Electrical communication can cause errors in electrical noise, resulting in decreased communication speed. However, optical communication is not affected by noise, so it can transmit signals quickly.

Conclusion:


The ultimate goal of the future transmission network is to construct an all-optical network, which is to fully realize "optical fiber transmission instead of copper wire transmission" in the access network, metropolitan area network and backbone network. The backbone network and the metropolitan area network have basically realized the all-optical network. In the today that information society develops faster and faster, optical communication will inevitably facilitate the further advancement of network.

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 cablings, cloud programmers & checkers, and 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.
  
 

 

2018-02-10

100G QSFP28 Optical Transceivers: A Cost-effective Solution

The continuous and rapid development of the Internet as well as the desire of people for higher speed optical networks facilitated the vigorous development of the entire optical communications industry and strongly promoted the independent R & D and innovation in many core technologies including optoelectronic devices technologies. 100g optical transceiver is regarded as the product of this big data era.

The first generation of 100G optical modules is CFP optical module with very large volume, then CFP2 and CFP4 optical modules appears. CFP4 optical module is the latest generation of 100G optical module, the width is only 1/4 of CFP optical module. Its package size is not same as the QSFP + optical module. The QSFP28 optical module has a smaller package size than the CFP4 optical module, which means the QSFP28 optical module has a higher port density on the switch. The following are several 100G QSFP28 series optical modules:

Main Types of QSFP28 Optical Transceivers


100G QSFP28 LR4 is a 100Gb/s transceiver module designed for optical communication applications compliant to 100GBASE-LR4 of the IEEE P802.3ba standard. 



100G QSFP28 SR4 is a four-channel, pluggable, parallel, fiber-optic QSFP+ SR4 optical transceiver module for 100/40 Gigabit Ethernet, Infiniband DDR/EDR and 32GFC applications.



100G QSFP28 PSM4 is a four-channel, pluggable, parallel, fiber-optic QSFP28 PSM4 optical transceiver module for 100/40 Gigabit Ethernet and Infiniband DDR/EDR Applications.



100G QSFP28 CWDM4 is a 100Gb/s transceiver module which is designed for optical communication applications compliant with the QSFP MSA, CWDM4 MSA and portions of IEEE P802.3bm standard.



Of course, QSFP28 series also includes 100G QSFP28 AOC; these products have played an important role in the development of 100G.

Advantages of 100G QSFP28 Optical Transceivers


1. Power Consumption


The power consumption of QSFP28 typically is no more than 3.5W, while the power consumption of other 100G optical modules typically is between 6W and 24W. From this, the power consumption of QSFP28 optical modules is much lower power than other 100G optical modules.

2. Cost


Now the data center is mainly 10G network architecture, in which the interconnection solutions are mainly 10GBASE-SR optical module and duplex LC multimode fiber jumper. If the existing 10G network architecture based on the direct is upgraded to 40 / 100G network, it will save a lot of time and cost. Therefore, one of the major interconnection trends in data centers is to upgrade from 10G networks to 40 / 100G networks without changing existing duplex multimode infrastructure. In this case, the MPO / MTP branchable cable is undoubtedly the ideal solution for a 10G upgrade to 40 / 100G.

3. Bandwidth


The QSFP28 uses the advanced 100G transport technology to provide the data center with a connection between the chassis switch and the core network, providing up to 150% greater panel bandwidth density than the 40G QSFP solution.

Optical Module Test


When using optical modules, test performance is an essential step. Optical module is composed of transmitter and receiver, so when we test, it is generally divided into four steps, which mainly includes the transmitter and receiver test.

First, the transmitter part:


When testing, pay attention to the wavelength and shape of the transmitter output waveform, as well as the receiver's jitter tolerance and bandwidth. When testing the transmitter, note the following:

1. The quality of the input signal used to test the transmitter must be good enough. In addition, the quality of the electrical measurements must also be confirmed by jitter and eye measurements. Eye diagram measurements are a common way to check the transmitter's output waveform because the eye diagram contains a wealth of information that reflects the overall performance of the transmitter.

2.The output optical signal of the transmitter must be measured by the optical quality index such as eye pattern test, optical modulation amplitude and extinction ratio.

Second, the receiver part:


Unlike test transmitters, the quality of the optical signal must be sufficiently poor when testing the receiver that a light pressure eye pattern representing the worst signal must be created. This worst case optical signal must pass through jitter measurements and light Power test to calibrate.

1. Eye pattern test, this will ensure that the eye "eye" is open. Eye diagram testing is usually done at the depth of the bit error rate;

2. Jitter test to test different types of jitter;

3. Jitter Tracking and Tolerance, testing the internal clock recovery circuit to track the jitter.


All in all, testing light modules is a complex undertaking, but it is also an indispensable step in ensuring good performance. Eye diagram measurement is a widely used measurement method that can effectively test the transmitter of an optical module. The optical module receiver test is more complex, but also requires more testing methods. 

2018-02-04

Analysis of 100G Optical Transceivers from Another Point of View

With the development of science and technology, the application of optical communications products in real life is becoming more and more widespread. The demand for network technology is also getting higher and higher. Therefore, 100G optical transceivers are gradually appearing on the market. The development of 5G and Data Center further make the 100G optical transceivers become the mainstream of the optical transceiver market gradually. Perhaps you have had a certain understanding of 100G optical transceivers, but if we analysis 100G optical transceivers from another point of view, you will find something different.

Development Background of 100G Optical Transceivers


For the earliest developed 100G optical transceiver, the form factor is CFP, developed in 2010. At that time, IEEE launched 100G optical transceiver SR10, LR4 and ER4 three standards, separately aiming at the 100m, 10Km and 40Km transmission. Followed by that, the IEEE standard added the new 100G SR4 project, but in 2013 did not reach consensus and vacancies. By 2016, the 100G optical transceivers used by various data centers were mostly the 25Gbps Serdes program, and the 100G optical transceivers that use the 50Gbps Serdes planned slowly appeared.

The Facing Problems for 100G Optical Transceivers


1. Channel Distance: The DWDM system supporting the 50GHz wavelength distance is very extensive. The 100G optical transceiver needs to meet the condition of supporting the 50GHz wavelength distance, therefore, the pattern of high spectral power should be used.

2. OSNR (optical signal-to-noise ratio): Under the same pattern, 100G optical transceivers requires10dB higher than 10G optical transceivers and 4dB higher than 40G optical transceivers. Therefore, a low OSNR tolerance code and high coding gain FEC algorithm are needed.

3. CD Margin: Under the same conditions, 100G optical transceiver dispersion tolerance only needs 1/100 of 10G optical transceiver, accounting for 16/100 of 40G optical transceiver. Therefore, 100G optical transceivers can use dispersion compensation technology, in the electric field or the optical domain compensation to complete the dispersion compensation for each wavelength.

4. PMD Tolerance: Under the same conditions, PMD (polarization mode dispersion) tolerance of 100G optical transceiver is 1/10 of 10G optical transceivers, accounting for 4/10 of 40G optical transceiver, so you need to choose coherent reception plus digital signal processing.

5. Nonlinear Effects: Compared with 10G / 40G optical transceiver, the nonlinear effects of 100G optical transceivers are messier.



The Types and Advantages of 100G Optical Transceivers


The main form factors of 100G optical transceiver include: CFP, CFP2, CFP4 and QSFP28. To compare their advantages, the main factor to consider is the costs and power consumption for Data Centers.

1. CFP optical transceiver supports all C-band wavelengths tunable and can complete the link detection, which use a common optical dual-binary modulation format ODB, convenient layout, power consumption is less than 24W.

2. The volume of CFP2 optical transceiver is one-half of CFP, its integration is 2 times CFP. It can complete the wide dynamic input range based on SOA to achieve stable admission sensitivity, support a full CFP optical transceiver, its low power consumption is lower than 9W.

3. The volume of CFP4 optical transceiver is one-half of CFP2, its integration is twice that of CFP2, front panel port density is also doubled compared with CFP2. CFP4 optical transceiver follows the MSA protocol, support the same rate as CFP/CFP2. Its transmission power increases significantly, but the power consumption drops significantly, only about half of the original, the system cost is lower than the CFP2. In addition, CFP4 optical transceiver uses 4 * 25 forms, through the 4 * 25G channel, complete 100G transmission. The transmission power is higher with higher stability.

4. The form factor of QSFP28 optical transceiver is smaller than the CFP4 optical transceiver. QSFP28 optical transceiver power consumption is generally not more than 3.5W, the use of QSFP28 optical transceiver can directly upgrade from 25G to 100G not through 40G, and therefore the cost is lower.


Types
Standard
The Largest Transmission Distance
Connector
Channel
Wavelength
Fiber Types
CXP
SR10
100m
MPO24
12*10G
850nm
MMF
CFP/CFP2/CFP4
(CFP4 doesn’t support SR10)
SR10
100m
MPO24
10*10G
850nm
MMF
LR4
10km
Dual LC
4*25G
1310nm
SMF
ER4
40km
Dual LC
4*25G
1310nm
SMF
ZR4
80km
Dual LC
4*25G
1310nm
SMF
QSFP28
SR4
100m
MPO12
4*25G
850nm
SMF
LR4
10km
LC
4*28G
1310nm
SMF
ER4
40km
LC
4*25G
1310nm
SMF
ZR4
80km
LC
4*25G
1310nm
SMF
CWDM4
2km
Dual LC
4*25G
1310nm
SMF
PSM4
2km
MPO
4*25G
1310nm
SMF


Conclusion 


Learning the contents of the 100G light module, above, do you have any further information? From the development trend, QSFP28 optical transceiver and CFP series optical transceiver are 100G network hot solutions, and the use of CXP will be less and less. Gigalight, as a veteran optical transceiver manufacturer with professional technology, advanced R & D capability and stable manufacturing capability, not only has many popular 100G optical transceiver products, like 100G QSFP28 CWDM4, 100G QSFP28 PSM4, CFP2 100G LR4, and etc. but also will release more new 100G optical transceivers in the first quarter of this year. More information about 100G optical transceivers, please visit the official website.