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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

10GBASE-T-Copper-applications-and-use-cases

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.

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

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.

F2F-10G-Multimode-to-Single-mode

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.

Conclusion

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.

Original Source : Single-mode Fiber Work Over Multimode SFP Transceiver

QSFP+ to SFP+ Adapter (QSA) Module Vs. QSFP+ to SFP+ Breakout Cable

People frequently ask about feasible solutions between 10G and 40G servers. QSFP+ breakout cables like QSFP+ to 4 SFP+ cables and MTP to 4 LC harness cables are the commonly used equipment to connect between QSFP+ ports and SFP+ ports. But recently, Cisco launched a new type of product—QSFP+ to SFP+ Adapter (QSA) module that could provide a smooth migration to 40 Gigabit Ethernet. Is it a better solution for the 10G to 40G migration? Should I use the QSA module or 40G QSFP+ breakout cable? This article will answer the above questions and provide some suggestions to you.

QSA Module—Is It a Better Solution for the 40G Migration?

The QSFP+ to SFP+ Adapter module, specified by Cisco, is the module built in QSFP+ form factor with a receptacle for SFP+ cable connector at the back (seen in the below image). When connecting the QSFP port to an SFP+ port, QSA module usually acts as an interface for SFP+/SFP cables. That means you can effectively plug in an SFP+/SFP optics operating at a 10 Gbps port on this module, then inserting the module into a QSFP port cage to realize the 40G Ethernet transition. QSFP+ to SFP+ adapter module ensures the smooth connectivity between 40 Gigabit Ethernet adapter and 10 Gigabit hardware using SFP+ based cabling. Therefore, once the QSA module came out in 2016, it was soon considered as the effective solutions for converting 40G ports to the 10G ports.

Cisco QSFP+ to SFP+ adapter cable

40G QSFP+ Breakout Cables Overview

People usually use either the QSFP+ to 4 SFP+ breakout cables or MTP to LC harness cables to convert the downlink 40G port of ToR (Top of Rack) access layer switch into 4x10G fan out mode, then connect to the 10G cabinet server port. QSFP+ to SFP+ breakout cable including the direct attach copper cable (DAC) and active optical cable (AOC) consists of a QSFP+ connector on one end and four SFP+ connectors on the other end. The cables use high-performance integrated duplex serial data links for bidirectional communication on four links simultaneously.

QSFP+ to SFP+ breakout cable

While the MTP to LC harness cable have one one MTP cables on the one end and four LC connectors on the other end. This type of cable is recommended to be used in the same rack within the short distance. The picture above shows the direct connectivity between the QSFP+ transceivers and SFP+ transceivers by using the MTP to LC harness cable.

QSA Module or QSFP+ Breakout Cable

In this part, I will make a comparison between QSFP+ to SFP+ adapter modules and QSFP+ breakout cables from the aspects of cost, performance and compatibility.

Cost—QSFP+ Breakout Cables Wins

QSFP+ to SFP+ adapter module is not certificated by Multi-source Agreement (MSA), but a sole source paradigm defined by few vendors. The only vendor owns its patent, so the QSA modules on the market are quite expensive. Nevertheless, QSFP+ breakout cables covered in the MSA standard, support both copper and optical connectivity, which are much cheaper than QSA modules. Cost comparison between QSA module and QSFP+ breakout cable (DAC, 1m) is listed in the below table.

cost comparison between QSA module and QSFP+ breakout cable

Performance

With QSA module, users have the flexibility to use any SFP+/SFP optics to connect to the 40Gbps data rate with a single 10G connection. However, QSA module only exists in 10G-40G speed, which also explains the reasons of its unpopularity of the market. QSFP+ to 4 SFP+ breakout cables split the 40G channel into 4x10G channel which provide four times more data transfers than QSA module does.

Compatible Switch and SFP/SFP+ Modules

QSA modules, according to Cisco, are available in 40 Gigabit Ethernet compatibility matrix. Cisco SFP/SFP+ transceivers that can be plugged into the QSA modules are concluded as Cisco 10GBASE-SR, LR, ER, ZR, DWDM SFP+, FET-10G and 10G SFP+ cable as well as SFP (1000BASE-T, SX, LX, EX, ZX). As for the QSFP+ to SFP+ breakout cables, different vendors have different compatible issues. Keep in mind that you should find the reliable fiber optic transceiver manufacturers.

Reminder:

  • Before using the QSA modules or the QSFP+ breakout cables to connect a 40 Gigabit Ethernet port to a 10 Gigabit SFP+ port, you must enable the fan-out mode of your devices.
  • Not all the 40G cards and switches can be split into 4x 10Gb mode, for example, the Mellanox QSFP cards do not support the QSFP to SFP+ breakout, but their switches can.
  • With the QSA module, you can directly use the SFP+ modules in a QSFP+ port, but you cannot use the QSFP+ optical cables in a QSA setup.
  • Telecom industry has been modified rapidly. Hence, it is more cost-effective to make additional investment in high-speed switches instead of breakout cables and expensive QSA modules.

Conclusion

Both the QSFP+ breakout cables and QSA modules provide a smooth migration to the 40 Gigabit Ethernet. With these optics, you can reuse the existing 10G SFP+ cables, optical transceivers and switches when upgrading to 40G Ethernet. QSFP+ breakout cables is regarded as the cost-effective and reliable solutions for the most situations, but QSA module is preferable for the application with a single 10G connection.

Original source: QSA Module Vs. QSFP+ to SFP+ Breakout Cable – Chinacablebuy