Category: Fiber Transceivers

Optical transceivers, Active Optic Cables, data center switches, and cable management in data centers.

Can I Use SFP Transceiver in SFP+ Slot?

by http://www.fiber-mart.com

A common confusion about SFP and SFP+ compatibility is that if I can use the SFP module in SFP+ slot. When I connect the SFP transceiver to SFP+ transceiver, can SFP+ negotiate down to 1G? Or is it possible to use SFP+ module in the SFP port on my switch? Can SFP+ copper twinax cable can negotiate down to 1G to support SFP? Can 1G and 10G can exist in the same link? All these questions usually create a giant headache for many engineers. After looking up many relevant documentation, now I will conclusion the answers in this article.
SFP Can be Plugged into SFP+ Ports in Most Situations
I’m not sure about the specific switch model, but as a general rule of thumb, SFPs will work in SFP+ slot, but SFP+ optics do not work in SFP slots. It’s just a power availability thing. When you plug the SFP module in SFP+ port, the speed of this port is 1G not the 10G. And sometimes this port will lock the speed at 1G until you reload the switch or do some fancy set of commands. Besides, the SFP+ port usually can never support speed under 1G. That is to say, we can’t plug the 100BASE SFP in the SFP+ port. In fact, for this question, it may depend greatly on the switch models – sometimes SFPs are supported in SFP+ ports, and sometimes not. For example, almost all SFP+ ports of Cisco switch can support SFPs and many SFP+ ports of Brocade switch only support SFP+. Though it’s feasible often, it’s safer to ask your switch vendor for some information.
SFP+ Can’t Auto-negotiate Down to 1G to Support with SFP Module
To my knowledge, unlike copper SFPs which are available in 10/100/1000 auto-negotiation, optics such as SFP and SFP+ do not support auto negotiation at all. In fact, Most (95+%) SFPs and SFP+s will only run at the rated speed, no more, no less. Besides, there is no such thing as a SFP+ that does 1G on one side (towards the fiber) and then does 10G on another side (towards the unit). Though we can use SFP in SFP+ ports in many cases, that doesn’t mean a SFP+ plugged into the SFP+ slot can support 1G. In a fiber link, if we plug a SFP in the SFP+ port on one side (1G), and then plug a SFP+ in the SFP+ port on the another side (10G), this may not work! You just can’t have 10 GbE at one end and 1 GbE at the other. For this question, if you use SFP+ copper, it also can’t negotiate down to 1G.
When use SFP and SFP+ modules in your network, make sure the speed of both ends of the fiber link is the same. SFP modules may can be used in SFP+ slot, but a SFP can never be connected to a SFP+ module. For their different speeds, transmission distance and wavelength. 10 SFP+ only can use for 10G SFP+ port, and can never auto-negotiate to 1G.

Full CWDM Mux Demux and CWDM SFP Transceivers Solutions

by http://www.fiber-mart.com

CWDM systems have channels at wavelengths spaced 20 nanometers (nm) apart, compared with 0.4 nm spacing for DWDM. This allows the use of low-cost, uncooled lasers for CWDM. In a typical CWDM system, laser emissions occur on full eighteen channels at eighteen defined wavelengths: 1610 nm, 1590 nm, 1570 nm, 1550 nm, 1530 nm, 1510 nm, 1490 nm, 1470 nm, 1450 nm, 1430 nm, 1410 nm, 1390 nm, 1370 nm, 1350 nm, 1330 nm, 1310 nm, 1290 nm, 1270 nm. Besides, for CWDM systems an industry standard color coding scheme is used. The latches of the CWDM SFP transceivers match the colored port indicators on the passive units therefore guaranteeing simple setup. Following color codes and wavelength are valid for CWDM.
Full CWDM Channels (18 Channels) Mux Demux Solution
The WDM system uses a multiplexer at the transmitter to combine several wavelengths together, each one carry different signal with bite-rate up to 10G and a demultiplexer at the receiver to split them apart. Both mux and demux are passive, requiring no power supply. The 18 Channels CWDM mux demux covers all channels of 1270nm to 1610nm in 20nm increments. Without replacing any infrastructure, it totally support data rates up to 180 Gbps by being completely protocol transparent. The main fields of applications are the use in SDH (STM-1, STM-4, STM-16, STM- 64), IP (Fast Ethernet, Gigabit Ethernet, 10 Gigabit) ATM and storage (1G, 2G, 4G, 8G, 10G Fibre Channel) networks. Connectors, located on the front of the CWDM mux demux modules, are labeled and use the same color-coding that is used to indicate the wavelength of the individual CWDM SFP transceivers (shown in the figure below).
When fiber availability is limited, CWDM mux demux could increase the bandwidth on the existing fiber infrastructure. By using 18ch CWDM mux demux mentioned above and the CWDM SFP transceivers, up to 180 Gbps could be supported on a fiber pair.
Full CWDM SFP Transceivers Solution
CWDM SFP transceiver is based on the SFP form factor which is a MSA standard build. The max speed of this product is 1.25G and they are also available as 2.5G and of course the popular CWDM 10G SFP transceivers. The CWDM SFP transceiver has a specific laser which emits a “color” defined in the CWDM ITU grid. The CWDM ITU grid is defined from 1270 to 1610nm and has steps of 20nm. So the available wavelength is 1270nm, 1290nm, 1310nm, 1330nm, 1350nm, 1370nm, 1390nm, 1410nm, 1430nm, 1450nm, 1470nm, 1490nm, 1510nm, 1530nm, 1550nm, 1570nm, 1590nm and C. Besides, our CWDM SFP transceivers are similarly color-coded as the CWDM mux demux to help you match the right link connection (shown in the figure below).
We can make the CWDM SFP transceivers compatible with every brand (Cisco, HP, H3C, Juniper, Huawei, Brocade, Arista). A lot of brands have vendor locking and only with the proper coding. fiber-mart is specialized in this rebranding or recoding. We have many different switches and routers in our test lab to test the coding. We also use different Optical Spectrum Analyzers to ensure the CWDM SFP transceiver is emitting the right color and has the correct power budget. The CWDM SFP transceiver is used in combination with passive CWDM mux demux, and we can provide you a complete solution and advice on which equipment fits best in your project. Please give us your project details and we will provide the most efficient and economical solution.

Can I Connect Fiber Optic Transceivers of Different Brand?

by http://www.fiber-mart.com

Data centers generally accommodates hundreds or even thousands of network switches, it happens when you have to connect switches from different vendors (i.e. switch X from Cisco and switch Y from HP). As the switches only fit their own brand-based fiber optic transceiver, the main issues thus falls into this: is it possible to contact two different vendor’s fiber optic transceiver module and form a viable link? The answer is yes – but you still have to take some critical aspects into account.
Case Study: Standard of Fiber Optic Transceiver is the Key
Sometimes people have to mix switches and fiber optic transceivers, mainly because the following reasons:
They already have brand X and they need more switches and they shop on price. Hence different brands
They need to replace switches but do not have money for all and they buy brand X and plan on going to brand X completely but it takes time to get there.
There exist quite a lot standards and protocols concerning fiber optic transceiver. Although many installers are very familiar with linking different vendor’s switch, the others are still worried that the incompatibilities of two transceivers may impede the link performance. They may come across the questions like “Can I order a 1000BASE-LX transceiver from any source and it will be compatible with all others 1000BASE-LX?” or “Would a link with a Juniper 1000Base-LX and a Cisco 1000BASE-LX transceiver work?”
Ideally it should work. 1000BASE-LX is a standard the same way 1000BASE-T is, except that it uses fiber as the transmission medium. You’ve already known that any copper interfaces with 1000BASE-T is interoperable since they are defined by the same 1000BASE-T standards. So you can expect the same with fiber 1000BASE-LX interfaces –  which are all defined by 1000BASE-LX. While this is true on the fiber side of the system, and should be true on the thing with the fiber optic transceiver socket. In fact, you can rest assure as SFP is multi-vendor standard that specified by a multi-source agreement (MSA). And it is a popular industry format jointly developed by many network component vendors.
Further Consideration of Fiber Optic Transceivers: Protocol, Transmission Wavelength and Cable Type
Connecting SFP optical transceivers from two different vendors still have some other restriction, since SFP transceivers differs from one another in protocol, interface type and transmission distance.
Ethernet Protocol: You have to pay attention that you use fiber optical transceiver of the same protocol at each end, for example: both sides with SX, LX or whatever is currently in use. Otherwise, you have to undertake the risk of link failure.
Cable Type: The fiber optic transceivers on each end must use the same fiber type. An SFP made for multimode fiber isn’t going to work well, if it does at all, with single-mode fiber. Same applies with other multimode fiber types: although mixing various 50 um fibers (OM2 and OM4) may work OK depending on data rate and distance. As long as each end is the same fiber type, you can mix vendors and even connector types, such as SC on one end and LC on the other end.
Wavelength: It is vital the wavelength of the fiber optic transceivers (850nm, 1310nm) matches on each end, as a 1310nm transceiver will NOT talk to a 850 nm transceiver. MMF has a lot of loss, and the wrong wavelength may cause loss and degradation on the longer runs. As for SMF, you need to be even more careful about wavelengths though, especially for long distance. So, if you are on the working range, all the fiber optic transceiver will work normally.
wavelength for optical transceiver
Conclusion
It is hence safe to say that when connecting two fiber optic transceivers from different fiber optic transceiver manufacturers, you can expect your fiber patch cable to lead a consistent link as long as you use modules of the same Ethernet protocol, cable type and working wavelength. fiber-mart provides fully compatible optical transceivers with affordable price and decent performance. For more information, please visit http://www.fiber-mart.com.

The Chanllenges of Technology And Cost 100G Faced

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More and more high bandwidth services such as high definition(HD) video, online games and video conference challenging the traditional network, 100G as a ease network bandwidth technology, becomes the new hope of the operator.
100G industry chain has matured, with all components and subsystems have commercial capacity of multiple manufacturers, the market also needs the support of 100G system, the backbone network will be fully transferred to the 100G-leading era. From the early 2013, the focus point of 100G is from the laboratory into 100G network deployment and the commercial 100G has started.
Four Technical Challenges Of 100G
Although the 100G has been carried out, but the 100G transmission technology meets four technical challenges.
First, high power consumption. The achievement mechanism of 100G technology is complex, the optical receiver requires the use of coherent reception and processing of the DSP, the key chip has no ASIC, resulting in high power consumption of the whole 100G system. When large-scale commercial 100G technology, the average power consumption of each wavelength is still a problem waiting to be solved. Currently the power consumption of per wavelength is above 200W, the average power consumption of per frame is 7000W, so there will need three frames. Obviously, the 28nm process can help to reduce energy consumption, but there is no 100G solution of 28-nanometer. In addition, although the light energy consumption is not large, but due to the use of next-generation optical transceiver will increase greatly, reducing the power consumption is very necessary.
The second is integrated, especially in the field of optical circuit and photoelectric integration. How to add mass active and passive optical devices such as laser, optical amplifier, wavelength division multiplexing(WDM) and transmitter/receiver to the network to achieve highly integrated? Using semiconductor technology to the integration of CWDM and laser?
The third is test. The challenges of 100G testing include the quality evaluation of the deployed 100G system signal and the system maintenance after deployed. 100G using polarization multiplexing, and the signal spectrum is wide, the common OSDR and test instruments can not real-time test it, only by shutting off the laser method. How to achieve real-time test is industry’s future research topic, many of today’s online testing system are worth studying.
The Fourth is few prospective studies. How to make the current transmission system gradually shift to user-oriented management from the traditional network management? Quickly and efficiently allocate the physical resources?
The key is the problem of cost
The key reason why 100G failed to be applied large-scale currently is the opportunity cost is relatively too high. In the era of 100G, the cost of optical module is very high. The mainstream CFP module, the actual sales price is more than $10,000. From the point of optical module cost, 100G module is several times higher than 10G optical module. It also requires manufacturers continue to make efforts in chip integration, integrated optical module miniaturization and system design, to achieve the overall cost of products are reduced.
Especially the regard of optical module technology, the cost of this part is the key of the whole 100G system cost, the optical module itself has to face the challenges of control power consumption and improve board integration.

Can I Use the QSFP+ Optics on QSFP28 Port?

by http://www.fiber-mart.com

100G Ethernet will have a larger share of network equipment market in 2017, according to Infonetics Research. But we can’t neglect the fact that 100G technology and relevant optics are still under development. Users who plan to layout 100G network for long-hual infrastructures usually met some problems. For example, currently, the qsfp28 optics on the market can only support up to 10 km (QSFP28 100GBASE-LR4) with WDM technology, which means you have to buy the extra expensive WDM devices. For applications beyond 10km, QSFP28 optical transceivers cannot reach it. Therefore, users have to use 40G QSFP+ optics on 100G switches. But here comes a problem, can I use the QSFP+ optics on the QSFP28 port of the 100G switch? If this is okay, can I use the QSFP28 modules on the QSFP+ port? This article discusses the feasibility of this solution and provides a foundational guidance of how to configure the 100G switches.
For Most Switches, QSFP+ Can Be Used on QSFP28 Port
As we all know that QSFP28 transceivers have the same form factor as the QSFP optical transceiver. The former has just 4 electrical lanes that can be used as a 4x10GbE, 4x25GbE, while the latter supports 40G ( 4x10G). So from all of this information, a QSFP28 module breaks out into either 4x25G or 4x10G lanes, which depends on the transceiver used. This is the same case with the SFP28 transceivers that accept SFP+ transceivers and run at the lower 10G speed.
QSFP can work on the QSFP28 ports
A 100G QSFP28 port can generally take either a QSFP+ or QSFP28 optics. If the QSFP28 optics support 25G lanes, then it can operate 4x25G breakout, 2x50G breakout or 1x100G (no breakout). The QSFP+ optic supports 10G lanes, so it can run 4x10GE or 1x40GE. If you use the QSFP transceivers in QSFP28 port, keep in mind that you have both single-mode and multimode (SR/LR) optical transceivers and twinax/AOC options that are available.
In all Cases, QSFP28 Optics Cannot Be Used on QSFP+ Port
SFP+ can’t auto-negotiate to support SFP module, similarly QSFP28 modules can not be used on the QSFP port, either. There is the rule about mixing optical transceivers with different speed—it basically comes down to the optic and the port, vice versa. Both ends of the two modules have to match and form factor needs to match as well. Additionally, port speed needs to be equal or greater than the optic used.
How to Configure 100G Switch?
For those who are not familiar with how to do the port configuration, you can have a look at the following part.
How do you change 100G QSFP ports to support QSFP+ 40GbE transceivers?
Configure the desired speed as 40G:
(config)# interface Ethernet1/1
(config-if-Et1/1)# speed forced 40gfull
How do you change 100G QSFP ports to support 4x10GbE mode using a QSFP+ transceiver?
Configure the desired speed as 10G:
(config)# interface Ethernet1/1 – 4
(config-if-Et1/1-4)# speed forced 10000full
How do you change 100G QSFP ports from 100GbE mode to 4x25G mode?
Configure the desired speed as 25G:
(config)# interface Ethernet1/1 – 4
(config-if-Et1/1-4)# speed forced 25gfull
How do you change 100G QSFP ports back to the default mode?
Configure the port to default mode:
(config)# interface Ethernet1/1-4
(config-if-Et1/1)# no speed
Note that if you have no experience in port configuration, it is advisable for you to consult your switch vendor in advance.
Conclusion
To sum up, QSFP+ modules can be used on the QSFP28 ports, but QSFP28 transceivers cannot transmit 100Gbps on the QSFP+ port. When using the QSFP optics on the QSFP28 port, don’t forget to configure your switch (follow the above instructions). To make sure the smooth network transmission, you need to ensure the connectors on both ends are the same and no manufacturer compatibility issue exists.

100G PAM4 QSFP28 or Coherent CFP?

by http://www.fiber-mart.com

The ever-increasing need for higher data rate in mobile data traffic, data centers and cloud services has pushed the access streams from 2.5Gb/s to 100Gb/s, and is demanding for 100Gb/s beyond without a stop. In today’s core network that has deployed 100G rates, there are QSFP28 optical transceivers including SR4, PSM4, CWDM4, LR4, ER4, etc., serving for a maximum 25km transmission distance. And there are 100G AOC, DAC and breakout cables generally for applications of tens of meters. 100G CFP/CFP2 modules including SR10, LR4 and ER4 support transmission distances of 150m to 40km. Until recent years, the telecom service providers are adopting new 100G DWDM technologies in their high capacity and long distance backbone applications. Coherent 100G DWDM transceivers are the first to be deployed for 100G long-haul applications, and then new technologies like PAM4 (Pulse Amplitude Modulation) are developed to meet lengths requirements for 100G metro network. This post is to discuss the issues on coherent and 100G PAM4 DWDM transceivers.
Overview on 100G DWDM Transceivers
In the past few years, the adoption of 100G DWDM technologies is mainly focused on coherent DWDM optical transceivers, including CFP and CFP2. Until the year 2016, Inphi (a specialist in this area) offers pluggable 100G PAM4 QSFP28 DWDM transceivers to support 80km data center interconnect (DCI). The alternative for 100G DWDM coherent transceiver is given much attention. Besides, this new option for 100G DWDM transceiver also arouses hot discussion on which to choose. Knowing the characteristics and suited applications of them could help in selection.
100G PAM4 QSFP28 and Coherent CFP/CFP2
There are significant differences between QSFP28 PAM4 transceivers and coherent CFP/CFP2 transceivers, but they also have some relations in 100G applications. Contents below will go to details of these optical modules.
QSFP28 PAM4
Before the announcement of PAM4, binary NRZ (non-return to zero) modulation format is used for 40G and 100G long-haul transmission systems. PAM4 has four distinct levels to encode two bits of data, essentially doubling the bandwidth of a connection. Currently the single-wavelength PAM4 modulation scheme is considered the most cost-effective, efficient enabler of 100G and beyond in the data center. The 100G DWDM transceiver utilizing PAM4 signaling is in QSFP28 form factor. The advantage is that the customers who want to build an embedded DWDM network can use this transceiver directly in the switch. On this side, it is simple and cost-effective solution. But there are some prerequisites: it needs amplification to get out of the blocks and dispersion compensation to go beyond 5-6km. Therefore, a separate DWDM multiplexer with an amplification system and dispersion compensation is required to connect data canters together.
single wavelength 100G PAM4
In another case, if the QSFP28 PAM4 module is added to an existing DWDM network, it must be a network already having right dispersion compensation modules (DCMs) and amplification system in place; if it is not, changes are required when QSFP28 PAM4 is later added.
Coherent CFP
CFP digital coherent optics (DCO) have a high speed digital signal processing (DSP) chip built in. They do not require separate DCMs. This is what makes CFP different from QSFP28. Instead, they have electronic dispersion compensation built in. Although the built-in DSP requires more power and adds cost in components, it releases the switch vendors from adding DSPs to their equipment. Coherent CFPs enables transmission distance of more than 1000km between sites.
CFP2 analog coherent optic (ACO) is half the width of the CFP. Existing CFP2 coherent DWDM optical transceivers are analog and require a separate DSP on the host board to take the full advantages of the coherent features. So it is suited for switch vendors who have fitted such a DSP, but it adds additional cost and power consumption on the main board.
CFP2 digital coherent optic (DCO), expected to be released in the coming two years, is more optimized than CFP2 ACO in that it has built-in DSP. This component will open up to all switch vendors using CFP2 without DSP. With different coherent CFPs optional, customers can pay only for what they need when they need it.
100G PAM4 QSFP28 or Coherent CFP?
This really should depend on the applications. According to ACG research (an analyst and consulting firm that focuses on the service providers’ networking and the telecom industry), the 100G PAM4 solution and coherent DWDM solution, together with IEEE802.3ba, cover different portions of the optical fiber reach in the data center interconnect. So when deploying a long distance 100G DWDM network with DWDM transceivers, the required transmission distance and available equipment should be taken into consideration when choosing a suitable pluggable module.
IEEE, PAM4, OIF coherent optical reaches
Conclusion
Using pluggable transceivers for embedded DWDM, where the DWDM functionality is in the transceiver and not a separate DWDM converter platform, offers the ultimate solution in terms of cost and simplicity. Both 100G PAM4 QSFP28 and coherent CFP/CFP2 are all suited to this approach. They can be used for embedded DWDM networking or as part of an existing DWDM installation. They all enable the advantages of pluggable modules: simple installation, easy spares handling, lower cost of ownership and quick return on invest.