Wednesday, April 26, 2017

How to Choose Fiber Optic Cable for 10G SFP+ Optical Transceiver?

How to choose fiber optic cables for 10G SFP+ transceivers? It seems like a dumb question for most of the fiber optic technicians. However, there are still some people, especially the green-hand network installers, may not know the compatibility between fiber optic cables and optical transceiver modules. Today, I want to make a clear illustration of how to choose the right transmission media (OS2/OM3/OM4/Cat6/Cat6a) for 10G SFP+ optical transceiver modules.
Overview of SFP+ Optical Transceiver Module
Before coming to the main part of this article, let’s first have a brief overview of the SFP+ optical transceiver modules and 10G fiber & copper cables.
  • 10GBASE SFP+ optical transceivers
SFP+ optical transceivers, according to the IEEE standards, can be divided into several types, for example, 10GBASE-LRM SFP+, 10GBASE-LR, 10GBASE-ER SFP+, 10GBASE-ZR SFP+, 10GBASE-SR SFP+, 10GBASE-T SFP+. Each SFP+ optical transceiver type has its own specification and usage that are not be listed here. For more, please review the previous articles.
  • BiDi SFP+ Modules
Besides the above 10GBASE SFP+ modules, 10GBASE-CWDM SFP+, 10GBASE-DWDM SFP+ and SFP+ BiDi optical transceiver modules are also the most commonly used 10G SFP+ optics. SFP+ BiDi optical transceiver usually uses two different wavelength to achieve 10G transmission over one fiber. The most frequently used wavelength of BiDi optical module is 1310nm/1550nm, 1310nm/1490nm, 1510nm/1590nm.
  • CWDM/DWDM SFP+ Modules
The Coarse Wavelength-Division Multiplexing (CWDM) and Dense Wavelength-Division Multiplexing (DWDM) SFP+ optics are the convenient and cost-effective solution for the adoption of 10 Gigabit Ethernet in campus, data-center, and metropolitan-area access networks. This 10G fiber optic transceiver type can support up to eight channels of 10GbE over single-mode fibers for distance over 80km.
10G Fiber & Copper Patch Cables
Fiber optic cables can be categorized into two types: single-mode and multimode fiber optic cables. They have different core size and fiber optic transmission equipment, which makes them suitable in different applications. Single-mode fiber patch cables, or OS1/OS2 (OS1 is now not popular on the market) are normally used for long-distance transmission with laser diode based equipment.
OS2 OM4 Cat6a for 10G SFP+ module
Multimode fiber cables, or OM1/OM2/OM3/OM4, have a relatively large light carrying core, usually utilized for short-distance transmission with LED based equipment. OM1, with a core size of 62.5um, supports 1GB network within 300m. OM2 (50um) can support up to 10GB, with a distance of 600m. OM3 and OM4 are the laser-optimized multimode fibers, which can be used in 10GB network with a link length of 300m, 550m respectively. These types of optical cables can be also used on 40G/100G network utilizing a MTP/MPO connector.
Cat6/Cat6a cables are the Copper Ethernet Network cables used for 10G network. Compared with Cat5e (1 Gigabits of data) and Cat5 cables (10/100 Mbps), Cat6 is the Ethernet cable that can handle up to 10Gbps with the distance limited to 164ft. Cat6a is the advanced version of Cat6 cables that further reduce crosstalk, which makes it can support the full 328 feet of Ethernet cable.
Choosing Fiber Optic Cables for 10G SFP+ Optical Transceivers
As noted before, single-mode patch cables can be used for 10G 10GBASE-LRM SFP+, 10GBASE-LR SFP+, 10GBASE-ER SFP+, 10GBASE-ZR SFP+, 10GBASE-CWDM SFP+, 10GBASE-DWDM SFP+ and SFP+ BiDi modules.
Cable TypeConnectorMax Distance
10GBASE-LRM SFP+9/125 SMFLC Duplex200m
10GBASE-LR SFP+9/125 SMFLC Duplex10km
10GBASE-ER SFP+9/125 SMFLC Duplex40km
10GBASE-ZR SFP+9/125 SMFLC Duplex80km
CWDM SFP+9/125 SMFLC Duplex80km
DWDM SFP+9/125 SMFLC Duplex80km
SFP+ BiDi9/125 SMFLC/SC Simplex80km

Multimode fibers, especially the OM3 and OM4 cables, are supported for 10GBASE-SR SFP+ transceiver modules. The following chart displays the part No. of customized OM3 and OM4 cables.
Customized Part IDConnectorFiber ModePolish TypesJacketStock Length
17235LC Duplex50/125 OM4UPCPVC1m-30m (3ft-98ft)
17235LC Duplex50/125 OM4UPCLSZH1m-15m (3ft-49ft)
17235LC Duplex50/125 OM4UPCOFNP1m-15m (3ft-49ft)
12018LC Duplex50/125 OM3UPCPVC1m-30m (3ft-98ft)
12018LC Duplex50/125 OM3UPCLZSH1m-30m (3ft-98ft)
12018LC Duplex50/125 OM3UPCOFNP1m-15m (3ft-49ft)

Cat6 and Cat6a Patch cables can be only used on the 10GBASE-T SFP+ transceivers.
10GBASE-T RJ45 SFP+ Copper module
Keep in mind, the newly available SFP+ copper transceiver modules can only support up to 30m.
This article lists all the existing the 10G fiber & copper patch cables and SFP+ transceiver module types, as well as the guidance about how to select the right patch cables for 10G SFP+ optical transceivers. FS.COM offers a full range of SFP+ optical transceiver modules and patch cables. Please contact us if you need any help.

Monday, April 17, 2017

Comparing 10GBASE-T SFP+ Transceiver Module With SFP+ SR/LR Optics & SFP+ DAC Twinax Cables

1000BASE-T SFP modules are available on the market as soon as the certification of Gigabit Ethernet network. However, 10GBASE-T SFP+ modules, owing to the technology limit, have not been supplied by vendors to support 10G copper networks. Instead, IT managers tend to use the cost-effective SFP+ direct attach cables (DAC) for short-reach 10G applications. Today, here comes a big news—vendors like HPE, Prolab, and FS.COM begin to offer 10GBASE-T SFP+ transceiver modules. Do you feel curious about them? This article will unveil the mysterious point of the 10G copper transceivers, and make a detailed comparison with SFP+ fiber modules and DAC twinax cables.
10GBASE-T SFP+ Transceiver Modules
10GBASE-T SFP+ transceiver modules are designed to meet the requirement of 10G longer-reach applications. Compared with SFP+ twinax copper cables (maximum distance is 10m), SFP+ 10GBASE-T transceiver modules operate over Cat6a/Cat7 with a link length of up to 30m. Seen from the below image, SFP+ 10GBASE-T transceiver terminates with a RJ45 connectors, which can be directly used in the RJ45 ports of 10G switches and NIC cards. What’s more, 10GBASE-T SFP+ module is announced to have lower power consumption (2.5W) than SFP+ Twinax DAC cables (4-8W).
Figure 1 shows how to plug a Cat6 cables in a 10GbE SFP+ module.
SFP+ 10GBASE-T Module Vs. SFP+ SR/LR Transceivers
In order to have a better understanding of the 10G copper modules, let’s compare the SFP+ 10GBASE-T modules with SFP+ SR/LR Transceivers and SFP+ DAC Twinax cables.
Both of the SFP+ copper and fiber modules are hot-pluggable with a managed soft-start and are interoperable with any SFP+ cage and connector system. However, they have total different performance when plugging into the 10G switches. SFP+ 10GBASE-T module uses the Cat6a cables for a link length of 30 m over RJ45 connectors. SFP+ SR operates over OM3 cables with a distance of 300m over LC connectors. While SFP+ LR optics utilizes the OS2 LC duplex cables for a distance of 10 km.
Figure 2 shows the SFP+ 10GBASE-T Module (left) and SFP+ SR Transceivers (right).
Note that 10G SFP+ transceivers are nowadays much cheaper than the newly released 10G copper module. For your reference, at FS.COM, Cisco SFP-10G-SR is offered at $16, Cisco stable SFP-10G-LR is &34. While Cisco SFP-10G-T is $380.
SFP+ 10GBASE-T Module Vs. SFP+ DAC Twinax Cabling
Whether to use SFP+ 10GBASE-T module and Cat6a cables or directly use the SFP+ DAC twinax cables for 10G short-reach application, it depends on your own network infrastructure.
  • Linking Distance and Power Consumption
As noted before, the maximum linking distance of SFP+ 10GBASE-T module is 30m, while the SFP+ DAC twinax cable is 10m. Furthermore, SFP+ 10GBASE-T module have reduced the power consumption of 10G copper modules, which is a great news for the heavy-loaded 10G data center networks.
  • Costs
For 10G intra-rack connection, SFP+ DAC twinax cables obviously cost lower than SFP+ 10GBASE-T copper modules and cat6a cables do. And you should also count the expenditure of 10G switches and NIC cards. 10G switches that can support 10G RJ45 ports are not available nowadays.
  • Reliability
Compatible SFP+ Twinax cables have been used for years in 10G networks. So they are quite reliable. As for the SFP+ copper modules, RJ45 interface is rock solid. But many professionals said that technically it could work, but it is not supported for most of the switches. Thus, it is not popular nowadays.
Customers are very happy to see that there are new products kept coming out to keep in pace with the ever-increasing technology. SFP+ 10GBASE-T copper transceiver is introduced to have a better interoperability between existing fiber switches and 10G copper ports. Although there are still some unsolved problems of SFP+ 10GBASE-T transceiver module, we believe they will be solved in the near future.

Friday, April 14, 2017

How to Choose Fiber Optics for Mellanox ConnectX Ethernet Adapter Cards?

Mellanox ConnectX Ethernet adapter card provides high-performance networking technologies by utilizing IBTA RoCE technology, delivering efficient RDMA services and scaling in ConnectX-3, 4, 5, 6 EN 10/25/40/50/56/100/200GbE connection. The Mellanox ConnectX EN Ethernet card supports a full suite of software drivers like Microsoft Windows (including Windows 10), Linux distributions, VMware and Citrix XenServer. ConnectX Ethernet adapter card comes in several types for 10/25/40/50/56/100/200GbE network, such as ConnectX-3 EN, ConnectX-3 Pro EN, ConnectX-3 Pro EN 10GBASE-T, ConnectX-4, ConnectX-4 Lx EN, ConnectX-5 EN, ConnectX-6 EN adapter cards. In this article, we present an in-depth network-level performance evaluation of the Mellanox ConnectX Ethernet adapter cards and the supported fiber optic cabling.
Mellanox ConnectX Ethernet Adapter Card
Network Interface Card (NIC), also known as Network Interface Controller, Network Adapter, LAN Adapter or Physical Network Interface. All Mellanox 10/25/40/50/100/200 Gigabit Ethernet adapters deliver high-bandwidth and industry-leading Ethernet connectivity in enterprise data centers, high-performance computing, and embedded environments. From ConnectX-2 to ConnectX-6, Mellanox keep upgrading their Ethernet adapter cards to meet customers requirement.
Connectx-6 EN
ConnectX-6 EN—200Gb/s Adapter Card
ConnectX-6 EN 200Gb/s Adapter Card, launched last year, was the world-first 200Gb/s Ethernet network adapter card for Ethernet connectivity, sub-600 ns latency and 200 million messages per second. ConnectX-6 EN, seen in the image, provides two ports of 200Gb/s for Ethernet connectivity. As the first adapter to deliver 200Gb/s throughput, ConnectX-6 is the perfect solution to provide machine learning applications with the levels of performance and scalability that they require.
ConnectX-5 EN—Adapter Supporting 100Gb/s EthernetConnectX-5
ConnectX-5 just as the image shows, supports two ports of 100Gb/s Ethernet connectivity, sub-700 nanosecond latency, and very high message rate, plus PCIe switch and NVMe over Fabric offloads, providing the highest performance and most flexible solution for the most demanding applications and markets.
Table 1 presents the detailed information about Mellanox ConnectX-5 EN Ethernet Adapter Cards
Ordering Part No.DescriptionSpeedPortsConnectorsDimensions w/o Bracket
MCX515A-CCAT100GbE single-port QSFP28, PCIe3.0 x16, tall bracket, ROHS R6100GbE1QSFP2814.2cm x 6.9cm (Low Profile)
MCX516A-CCAT100GbE dual-port QSFP28, PCIe3.0 x16, tall bracket, ROHS R6100GbE2QSFP2814.2cm x 6.9cm (Low Profile)
MCX516A-CDAT100GbE dual-port QSFP28, PCIe4.0 x16, tall bracket, ROHS R6100GbE2QSFP2814.2cm x 6.9cm (Low Profile)
ConnectX-4 EN—Adapter Supporting 10G/40G/100Gb/s
ConnectX-4 LX ENConnectX-4 adapter cards have three different types: ConnectX-4 Lx EN Programmable Adapter Card, ConnectX-4 EN, ConnectX-4 Lx EN. ConnectX-4 Lx EN Programmable Adapter Card is listed in the right image. ConnectX-4 EN network is the single or dual port 100 Gigabit Ethernet adapter cards. ConnectX-4 Lx enables data centers to migrate from 10G to 25G and from 40G to 50G speeds at similar power consumption, cost, and infrastructure needs. If you are into this NIC card, you'd better look through their difference.
ConnectX-3 Pro EN—10/40/56 Gigabit Ethernet Network Interface Cards
ConnectX-3 Gigabit Ethernet interface card is one of the mostly used NIC cards nowadays. This kind of NIC card can support 10/40/56Gb/s Ethernet connectivitConnectX®-3 Pro Programmable Adapter Cardsy with hardware offload engines. The long-term goal at Mellanox ConnectX Gigabit Ethernet adapter card is to allow customers to wire once and switch protocols on the server and switch as required by workloads. Mellanox can presumably charge a premium for such capability, and ConnectX-3 silicon allows Mellanox to create fixed adapters and switches at specific speeds to target specific customer needs and lower price points, too. The image on the right display the ConnectX-3 Pro Programmable Adapter Cards.
For detailed information about ConnectX-3 Pro EN adapter cards, please see the Table 2.
Ordering Part No.DescriptionDimensions w/o Bracket
ConnectX-3 Pro EN Adapter Cards  
MCX311A-XCATSingle 10GbE SFP+10.2cm x 5.4cm
MCX312A-XCBTDual 10GbE SFP+14.2cm x 6.9cm
MCX313A-BCBTSingle 40/56GbE QSFP14.2cm x 5.2cm
MCX314A-BCBTDual 40/56GbE QSFP14.2cm x 6.9cm
ConnectX-2—Supporting 10G Ethernet Switches
ConnectX-2 Gigabit Ethernet Cards
Mellanox ConnectX-2 EN cards are the older cards for Ethernet only. That means that they will not work in Infiniband networks. In fact, there are still a few examples of OSes without ConnectX-2 support. Prime examples are FreeBSD 9.3 based FreeNAS and NAS4Free versions which did not have built-in support for the cards. The bottom line is that in terms of compatibility, one does need to verify these cards will work.
Many customers do use these in their Windows 10 home workstation for a 10Gb SFP+ back-haul network. Speeds are reliable and excellent. Nowadays, Mellanox does not supply this card, but ebay and Amazon do provide ConnectX-2 cards under $19.
How to Choose the Cables and Optical Modules for ConnectX-3 Ethernet Adapter Cards?
According to Mellanox, ConnectX-3 10G/40G/56G Ethernet adapter cards are interoperable with 10/40 Gb Ethernet switches. Passive copper cables with ESD protection are supported in this NIC card. ConnectX-3 cards can support up to 56Gb/s that can accommodate several fiber cables and optical transceiver types. Take the MCX313A-BCBT as an example, it has single 40GbE QSFP+ port. QSFP+ optical transceivers and DAC cables are feasible in this Ethernet Adapter Card. For the 10G SFP+ to 40G QSFP+ migration, Mellanox QSA (QSFP+ to SFP+) modules are required.
QSA Module
A previous article QSFP+ to SFP+ Adapter (QSA) Module Vs. QSFP+ to SFP+ Breakout Cable provides the detailed information about how to use the QSA module.
DAC Twinax or 10GBASE-T Copper Cable For ConnectX-2 NIC Cards
Mellanox ConnectX EN Gigabit Ethernet Cards can support up to 200Gbps data rate. Each ConnectX adapter card, as mentioned above, supports optical transceivers and modules applied for 10G/25G/40G/100G Ethernet network. ConnectX-2 EN Ethernet card, for example, can be used for 10GbE networks. Except the expensive SFP+ optical transceivers, SFP+ DAC Twinax and 10GBASE-T copper cables are the commonly used  transmission media for 10G data center inter-rack and TOR switching. So how to choose between them?
DAC Twinax Cable
DAC SFP+ Twinax cables integrates SFP+ modules and Twinax cables on the same conduit. It uses the SFP+ optical transceiver modules as connectors (not the real transceiver) on both ends so as to provide a cost-effective and low-power consumption solution for data center interconnection. 10G DAC Twinax cables can be divided into two types: active DAC twinax and passive DAC cables. For distances >5m and <10m, pickup the active version. Otherwise passive direct attach copper cables should be fine.
SFP+ DAC Twinax cables in NiC
Fiberstore is one of the best vendors for DAC and other fiber optics. Their packaging and after-sale support for even the smallest orders is excellent. For connecting two ConnectX-2 cards together, you can get one of the SFP+ copper cables.
Ethernet Network Cables
Ethernet Network Cables like Cat5, Cat5e, Cat6 do look alike from the outside and they all use the same connectors as well. However, they have significant differences on the inside. One simple method is that you can find out the type of cable you have by looking at the text printed on the side of the cable. There are other cables possible (like Cat7 and Cat8 cables) but Cat5, Cat5e, Cat6 cables are the most common now.
  • CAT5
Category 5 cabling is an older type of network cabling compared with Cat5e and Cat6 cables. Cat5 cables support transfer speeds of 10/100 Mbit/s (Fast Ethernet). Nowadays, many installers treat it as old and obsolete and try not to use it. For those who buy cat5 cables,  they tend to use in older devices such as an older router or switch.
Category 5 enhanced (Cat5e) cables currently are the most commonly used Ethernet network cables owing to its enhanced transmission data rate and reduced crosstalk. Cat5e cabling supports 1000 Mbit/s and cust down on external and internal crosstalk. It basically means that Cat5e is better at keeping signals on different circuits or channels from interfering with each other.
  • CAT6
Category 6 cabling (Cat6) supports 10 Gbit/s speeds with additional crosstalk improvements. If you're purchasing a new cable for future proofing,  it should really be CAT6 or above. That doesn't imply Cat6 cables protect your network from the future or anything, it just means it will keep it up to date for longer when the next products comes along.
Note : Your network speed depends on  the slowest part of your setup. If you want to deploy gigabit ports, gigabit routers, switches,  then please make sure you cabling also supports those speeds as well.
Mellanox is the world-class vendor for selling multi-protocol chips and adapter cards for servers. It provides a wide range of high-speed interconnection solutions including Gigabit Ethernet cards and InfiniBand adapter cards. The above mentioned ConnectX Gigabit Ethernet cards can not be used in InfiniBand networks. ConnectX Mellanox Gigabit Ethernet cards are the cost-effective devices for your network applications. If you do have the Mellanox NIC cards, you can buy the cost-effective DAC and optical transceiver modules from FS.COM to further reduce the total cost of your budget.

Thursday, April 6, 2017

How to Choose SFP Transceiver Modules for UniFi US-8-150W Switch?

Ubiquiti Networks Unifi switch is part of the UniFi line of products that delivers robust performance and intelligent switching for the growing networks. Many customers nowadays hold great feedback about the cost-effective UniFi switches. US-8-150W, as one of the most popular UniFi switches, offers eight Gigabit RJ45 ports and 2 SFP ports that can support up to 1Gbps. So, how to choose the suitable optics for UniFi US-8-150W switch? This article will provide detailed information about this UniFi switch and the appropriate SFP modules for US-8-150W switch (seen in the below image).
US-8-150W port info
Understanding UniFi US-8-150W Switches
Ubiquiti Networks UniFi switches can be divided into two types: managed Gigabit switches and managed PoE+ Gigabit Switches. In short, POE switches and non-POE switches. Each UniFi switch type is fully managed Gigabit switches with RJ45 and SFP+/SFP ports, offering non-blocking throughout switching performance.
US-8-150W UniFi switch features 8 RJ45 ports and 2 SFP ports which offer convenient different power output options, auto-sensing IEEE 802.3af/at POE/POE + performance. It is a bit larger than a standard home switch. So, would-be buyers who are looking to rack mount need to buy a extra shelf and stick it there. The table below provides the clearer information about this switch.
port info of US-8-150W
Note that US-8-150W is only US $199.
How to Select SFP Modules for UniFi US-8-150W Switches?
According to Ubiquiti Networks, both their original and third party SFP transceiver modules from other vendors can be used on UniFi switches.
Ubiquiti Networks UF-MM-1G & UF-SM-1G-S
Ubiquiti Networks only offer two type of SFPs—UF-MM-1G and UF-SM-1G-S. UF-MM-1G SFP module supports a data rate of 1.25 Gbps over multimode fibers. It uses the 850nm as the Tx and Rx wavelength with a supporting distance of 550m.
UF-SM-1G-S is a single-mode SFP available in both blue (1310nm) and yellow (1550nm) color code. Unlike the 1000BASE-LX SFP optics with LC single-mode fibers that can operate up to 5 km, UF-SM-1G-S only supports a link limit of 3 km.
Ubnt SFP and SFP+ modules
Figure 3 presents all the existing fiber optic transceivers (SFP and SFP+) from Ubiquiti Networks. UF-SM-1G-S is in the middle of the image.
3rd Party SFPs for US-8-150W Switch
Besides the above two SFP types, there are several more Gigabit Ethernet standards for SFP transceiver modules—1000BASE-T, 1000BASE-SX, 1000Base-LX/LH, 1000BASE-ZX, 1000BASE-BX-D, 1000BASE-BX-U and 1000BASE-EX, which are compatible with the UniFi switches. According to the Ubiquiti Networks, Fiberstore (FS.COM) SFPs are tested to be fully compliant with UniFi switches. For more information about these compatible SFPs, please check on the following list.
FS.COM compatible SFPs for UniFi switches
From the table, we know that several Cisco SFP modules and HPE SFP transceivers are working on the UniFi Switches. In our test center, we have tested the GLC-T compatibility and Cisco GLC-SX-MM compatible issues.
More Information About UniFi Switches
Besides the hot selling US-8-150W switches, there are a series of UniFi switches such as US-8-60W, US-16-XG, US-48, US-8, US-24, US-48-750W, US-48-500W, US-24-250W, US-24-500W. Whether you use which one, FS.COM SFPs in the above table are tested to be fully compatible with UniFi switches. For such a low price of the 3rd party SFP transceiver modules, it is advisable for you to purchase more optics for backup.
The UniFi US-8-150W switches are designed to be part of the complete line of small business or home networking and wireless communication products that work together as part of proven, fully integrated, easy-to-use small business solution. UniFi switches support several types of Gigabit Ethernet SFP optical transceivers. All these high-quality fiber optic transceivers can be found on FS.COM for great prices. We also make sure to provide its customers same day shipping. Some of the items can be directly shipped from Seattle warehouse.

Tuesday, March 28, 2017

QSFP28 Transceiver With MTP or LC Duplex Cables

Nowadays, QSFP28 transceiver is the mainstream of 100G optics market. So as to meet different 100G deployment needs, QSFP28 modules usually come in several standards such as QSFP28 PSM4, QSFP28 CWDM4, IR4, SR4 and LR4, etc . Compared with CXP and CFP 100G optical transceivers, QSFP28 optics are the smallest form factors that provide a high-density and high-speed solution for 100G networks. A previous article provide detailed information about what distance QSFP28 optics can support for 100GbE deployment. Today’s article will introduce 100G QSFP28 cabling solutions by the use of MTP/MPO cables and duplex LC cables.
QSFP28 modules offer four channels of high-speed differential signals with each data rates up to 28Gbps, and will meet 100 Gbps (4x25 Gbps) in the end. QSFP28 transceiver is available in 100GBASE-SR4, 100GBASE-LR4, PSM4 and CWDM4 standards. The interface of 100G QSFP28 transceivers includes MTP/MPO and LC duplex cables.
Cabling Solutions of QSFP28 MPO
100G QSFP28 100GBASE-SR4 and 100GBASE-PSM4 transceiver modules are the 100G transceiver modules that need to be connected with MTP/MPO interfaces. 100GBASE-SR4 QSFP28 complies with QSFP28 MSA and IEEE 802.3bm specifications. It can support a link length of 100 m. 100G PSM4 specification defines requirements for a point-to-point 100 Gbps link over eight single-mode fibers with a supporting distance of 500 m. Figure 1 shows the QSFP28 SR4 with MTP connector.
MTP/MPO fiber cable is commonly used to connect QSFP+ or QSFP28 transceivers with single-mode and multimode categories, which is specially designed for 40G/100G high-density data center cabling system. MTP/MPO fiber cables are usually terminated with 12-fiber, 24-fiber, 48-fiber MTP/MPO connectors. Single-mode MTP/MPO cable is able to carry signal over long distance while multimode is for short-reach application. QSFP28 mpo
  • 100GBASE-SR4 QSFP28 over Multimode MTP cable
100GBASE-SR4 QSFP28 works over a 12-fiber multimode MTP/MPO patch cable (four not used) for short-reach 100G connection. Figure 2 shows the direct connection between 100GBASE-SR4 QSFP28 modules by the use of Female to Female 12-Fibers OM4 trunk Cable.
  • 100GBASE-PSM4 QSFP28 Over Single-mode MTP Cable
Similar to 100GBASE-SR4 QSFP28, 100GBASE-PSM4 QSFP28 also requires 12-fiber MTP/MPO patch cable. But QSFP28 PSM4 matches with single-mode MTP/MPO fiber patch cable instead of the multimode MTP/MPO .patch cables.
100G QSFP28 Optics With Single-mode Duplex LC Interface
100GBASE-CWDM4 QSFP28 and 100GBASE-LR4 QSFP28 are the 100G modules designed for long-reach applications terminated with duplex LC interface. 100GBASE-CWDM4 QSFP28, as the name implies, it is a full duplex module with the use of CWDM technologies. It integrates transmit and receive path in one module. 4 lanes of optical signals (25 Gbps per lane) firstly are multiplexed into an LC duplex interfaces on the transmitting side. Then data streams are de-multiplexed by an integrated optical de-multiplexer and transformed to an electrical CAUI-4 output driver. QSFP28 CWDM4 can support a distance of 2 km over single-mode fibers. Figure 3 shows the interconnection of 100G QSFP28 LR4 module connected with MTP to LC breakout and MTP cassette to achieve a total 400G data rate transmission.
Cisco QSFP28 LR4 optics
100GBASE-LR4 QSFP28 is a 4x25Gbps transceiver module that can support link lengths up to 10 km. 100GBASE-LR4 QSFP28 also operates over single-mode fiber cable with duplex LC connector by multiplexing and de-multiplexing optical signals. Common single-mode duplex LC patch cable can meet the cabling requirement of these two transceivers. For high density data center, HD LC fiber patch cable is highly recommended as the push-pull tab is easy to remove and can save space.
With compact size and low power consumption, 100G QSFP28 modules are becoming the most popular 100G optics on the market. QSFP28 SR4 and QSFP28 PSM4 transceivers terminate with MTP/MPO interfaces, while QSFP28 LR4 and CWDM4 modules connect with LC duplex cables. Besides QSFP28 transceivers, there are QSFP28 DAC and AOC cable available for short-reach 100G connections.

Thursday, March 23, 2017

10GBASE-T SFP+ Copper Transceiver Module – Innovative But Controversial

The past few years have seen the broad adoption of 10Gbps connectivity at network edge equipment. SFP+ optics including SFP+ fiber devices and SFP+ direct attach copper (DAC) cables, dominates the 10Gbps connectivity solution in the core or spine due to the longer link lengths and higher aggregated data bandwidth, however, 10GBASE-T cable (Cat 6a/7) is proven to be unbeaten for its lower cost, ease of installation and reliable performance for 10Gbps edge network with a link length of 100 m. In order to get most of your cat6a cabling, last year HPE and some other vendors launched a 10GBASE-T SFP+ transceiver module, which claimed to give equipment designers and data center professionals a new option in architecting their network solution. This article will provide detailed information about the innovative but controversial SFP+ 10GBASE-T copper module from a positive point of view.
SFP+ 10GBASE-T Copper Transceiver—RJ45 connector, 30 m, 2.5 W
SFP+ 10GBASE-T copper transceiver is specifically designed for high-speed communication links that require 10 gigabit Ethernet over Cat 6a/7 cable with a link limit of 30 m. Compared with standard SFP+ SR/LR fiber optics, the added benefit is that it uses standard-based technology with the familiar RJ45 connector and provides backward compatibility with legacy networks.
SFP+ 10GBASE-T module usage
SFP+ 10GBASE-T transceiver, compliant with MSA standard, is the first transceiver that offers 10GbE communication over copper. Seen from the above image, you can directly plug the 10GBASE-T SFP+ module into SFP+ port of the NIC or switch. The power usage and heat generated for 10GBASE-T is 4-8 watts, but SFP+ 10GBASE-T copper transceiver consumes 2.5 watts. Obviously, the specification of SFP+ copper module has been optimized to save more than 0.5 W per port when compared to an embedded 10GBASE-T RJ45 port for link distances up to 30m.
Nowadays SFP+ 10GBASE-T transceiver, owing to the compatible issue with switches, is not offered by many vendors. However, from a network equipment designer’s perspective, 10G SFP+ copper modules will become popular in the near future.
The Innovative Points of SFP+ 10GBASE-T Transceiver Module
It is true that Cat 6/Cat6a cabling can provide limited support of 10GBASE-T in some environments, but the reality is that there are several compelling reasons to specify SFP+ 10GBASE-T copper modules in a new 10 Gbps-ready data center.
  • Smaller Form Factor: Interoperable with any SFP+ cage and connector system
  • Reliability: The RJ45 connector interface is rock solid. No surprises when deployed in your data center
  • Reach: Up to 30 m over Cat 6a UTP cable, sufficient for all network access use cases
  • Innovation: Hot-pluggable with a managed soft-start
  • Performance: Full PHY presentation, which means nothing is missing
  • Cost: Pay-as-you-grow model that performs for today and scales for tomorrow
The Controversial Points of SFP+ Copper Module
Q1: Vendors thought that it would never be possible to create a 10Gb copper transceiver as SFP+ specification use less power than 10GBASE-T requires. But theoretically, SFP+ 10GBASE-T copper module indeed reduces the power consumption of more than 0.5 watts.
Note that SFP+ 10GBASE-T transceiver module meets the SFP+ spec, but it is not meeting 10GBASE-T official spec.
Q2: With the cheap SFP+ DAC Twinax and reliable SFP+ fiber optics available for 10Gbps application, why should people use the SFP+ copper modules?
In terms of application, some server NICs and gears don’t work well with DAC twinax. In this case, instead of replacing all your copper devices into the fiber cabling, you’d better stick to the copper-based network. The following part displays two scenarios of 10G connectivity by using SFP+ copper modules.
Scenario 1: Use Case Between Server and Storage Appliance
Scenario 2: Use Case Between Edge Switches
Scenrio 2 network-upgrade-to-10G
From the technical point of view, 10G SFP+ copper twinax cable and 10G SFP+ modules share some differences in power consumption, latency, linking length and cost.
The power usage, latency and heat generated for 10GBASE-T is 4-8 watts, which is considerably higher than using DAC twinax or fiber optics (nearly 1 watt). SFP+ 10GBASE-T copper module, however, uses 2.5 watts (max). Furthermore, SFP+ DAC cables (both passive and active) can only support up to 10 m, but the SFP+ 10GBASE-T transceiver connected with cat6a cables can cover a distance of 30 m.
The low-cost of twinax DAC makes it a better choice for performance in ToR deployments. With 10m twinax you can usually cover up to 3-adjecent racks. While the existing SFP+ 10GBASE-T transceivers usually charge even higher than the regular SFP+ fiber optics. Besides, you should factor in the power and cooler requirement overhead that 10GBASE-T optics brings with it.
Q3: Is it reliable to use SFP+ 10GBASE-T modules in your network?
So far, customers still feel skeptical about this product. Many professionals said that technically it could work, but it is not supported for most of the switches.
Final Words
Data center managers are taking the advantages of the convenience and flexibility provided by deploying 10 Gbps technology over twisted-pair copper cabling and leveraging their investment in installed copper infrastructure. To have a great interoperability between existing fiber switches and those with 10G copper ports, 10G copper SFP+ is introduced. However, owing to the unsolved compatible issues and limited usage, customers nowadays still choose to use DAC Twinax or SFP+ fiber optics for 10Gbps connectivity. We believe, in the incoming future, all the problems will be solved.

Sunday, March 19, 2017

Will Single-mode Fiber Work Over Multimode SFP Transceiver?

Network installers usually come across a situation that device you have in your network does not always fit and work perfectly with the fiber. They plan to make a cable plant based on the multimode cabling, but owing to the link limitation or other reasons, they have to connect multimode equipment with single-mode devices. Is it feasible? Or put it more specifically, can I use the multimode SFP over single-mode fibers or vice versa? This article will give you a detailed illustration about the feasibility of the solutions, and introduce two relevant devices (mode conditioning cable and multimode to single-mode fiber media converter).
Single-mode Fiber Over Multimode SFP—You Can If You Are Lucky
This is the question that has been asked so many time, but no one can give the exact answer—yes or no. Hence, let’s illustrate it in details.
Most people think single-mode and multimode fibers are not interchangable because of the wave length of the laser and core size of the fiber. Single-mode fiber (MMF) uses a laser as a light source (the light beam is very concentrated), while multimode fiber (MMF) uses an LED to generate the signal. This would require two significantly different devices to generate the signal.
The core sizes are drastically different between SMF and MMF. SMF is 9 micron and multimode is 62.5 or 50 micron. If users try to mix the single-mode and multimode cabling in the same network, they might have trouble dealing with the two different types of signal.
However, it is possible to interconnect two devices using SMF interfaces at one end and MMF receiver at the other end. Keep in mind that it depends on the devices, so you can if you are lucky. When plugging LC single-mode duplex fibers on the multimode fiber transceiver (1000GBASE-SX) in the network, you will find the link came up (the light on the switch turns green). Therefore, the multimode fiber transceiver connected by the single-mode fibers works for short-reach application. The following image is the real screenshot of the single-mode fibers inserting into the 1000BASE-SX SFP.
real screenshot of inserting single-mode fiber over multimode fiber transceivers
While it should be stressed that the link is not reliable and it only works for particular brand devices with a very short link length. Many sophisticated vendors like Huawei, Alcatel or Cisco do not support it. Nevertheless, owing to the differential mode delay (DMD) effect, signal loss of this connection is not acceptable, either.
To sum up, this might be feasible but not advisable. If you need to make a connection between single-mode and multimode interfaces, you’d better use the intermediate switch that is able to convert the signals between single-mode and multimode fibers. The following part will introduce two solutions that might be helpful for the multimode and single-mode conversion.
Solution 1: MCP Cable—Single-mode In and Multimode Out
As to the multimode fiber with single-mode SFPs, most people mention the mode conditioning patch (MCP) cables. The MCP cable is launched to support 1000BASE-LX optics over multimode cable plant. The mode conditioning cables allow customers to successfully run Gigabit Ethernet over our multimode cable using single-mode fiber transceivers, Cisco 1000BASE-LX/LH SFP is the special type of transceiver that can both support single-mode and multimode fibers. The image below displays the difference between standard SC multimode patch cable and SC mode conditioning patch cable.
comparison between standard SC multimode fiber patch cable and SC MCP cable
Then, in this situation, you can run successfully from a single-mode fiber transceiver over multimode fiber with the use of MCP cables, but the distance will not exceed the link specification for multimode transceivers. Otherwise, there will be much signal loss in the cable run.
In general, if you want to run multimode fiber optic cable over 1000BASE-LX SFPs, you can use the mode conditioning cable. However, mode conditioning patch cords are required for link distances greater than 984 feet (300 meters). For distance less than 300 m, please omit the mode conditioning patch cords (although there is no problem using it on short links).
Solution 2: Fiber to Fiber Media Converter—Conversion Between Multimode and Single-mode Fibers
As noted before, mode conditioning cables, to some extent, can realize the connection between single-mode to multimode, but you can not say that you can convert single-mode to multimode or vice versa. Mode conversion between multimode and single-mode fibers often requires fiber to fiber media converters or the single-mode to multimode fiber converter.
In the above diagram, two Ethernet switches equipped with multimode fiber ports are connected utilizing a pair of fiber-to-fiber converters which convert the multimode fiber to single-mode and enable network connectivity across the distance between Gigabit switches.
It doesn't really make much sense to use the single-mode fiber transceivers with multimode fibers in your network or vice versa, although the link will come up. Like I said above, you can if you are lucky connect. MCP cables and fiber to fiber converter are the two available options for single-mode and multimode connection. If you bought the wrong fiber optic cables, just replace it into the right one. Fiber optic cables and optical transceivers modules nowadays are very cheap. You won’t need to risk of mixing them in the same network.