Author Archives: Alice.Gui

How to Build a Home Network?

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You may want to connect your desktops, laptops, printers and other machines at your home to the internet and achieve the information sharing. Perhaps you just want to connect your smart phone via WiFi when you’re at home to reduce the usage of your mobile data plan. To complete that, all you need to know is how to build a home network. There are lots of ways to set one up. I’ll introduce the basic setup for the most common case. For person that already have a network, I’II tell ways about how to expand the existing home network in this blog too.

Basic Wired Ethernet Connection

The basis of your home network will be Ethernet. This word has a very specific technical meaning, but in common use, it’s simply the technology behind 99% of computer networks. Most computers now come already equipped with an Ethernet adapter – it’s the squarish hole that accepts Ethernet cables.

ethernet-laptop

Usually, your broadband connection being cable, DSL, or something else will first go through some kind of device typically called a modem. The modem’s job is to convert the broadband signal to Ethernet. You’ll connect that Ethernet from your broadband modem to a broadband router. Router, as its name implies, is used to “route” information between computers on your home network and between those computers and the broadband connection to the Internet. Each of your computers already has an Ethernet adapter. An Ethernet cable will run from each computer to the router and another cable will connect the router to the modem.

Wired Ethernet Connections

Set up Wireless Connection

Most laptops and portable devices (and even a few desktops) support wireless connection via a technology known as WiFi. WiFi is a short-range wireless technology that you need to provide on your home network, if you want to be able to use it. The most common approach to include wireless capabilities in your network is by using a wireless router.

Wireless Connections

The wireless router combines the functions of two devices: the router, just as we saw before, and a wireless access point. A wireless access point, occasionally abbreviated WAP, is simply a network device that converts the wired Ethernet signals into wireless WiFi signals and vice-versa. Wireless routers are actually more common than their wired-only counterparts in the home and small business networking market. In fact, even if you don’t have a wireless device today, I typically recommend getting a wireless router anyway for future expansion.

Expand the Home Network Capacity

The number of internet-connected devices that we now deal with is pretty amazing. A typical wireless router or router with a wireless access point can easily handle dozens of devices connected wirelessly. However, wired devices may present problems. Many home routers – wired or wireless – come with only a limited number of connections. It’s common for there to be exactly five connections: one for the internet (“WAN” or modem) and then four for networked devices.

router-connect

If all you have is a four-port router, adding that fifth device looks like a problem. The simple solution is to use a switch. A switch is a semi-intelligent network extender. Its job is simply to make sure that data coming in on any port is sent to the other correct port to reach its intended destination. That’s really all it is. All ports on a switch are equal. In the example below, one port of the switch is connected to one of the ports on the router to which a computer might have been connected. Other computers are then connected to the switch. Switches come in many sizes and often add much more than just a few ports. Common configurations for the home include 8 or 16-port switches.

Expand Home Networks

Conclusion

Build a home network is very easy. Usually, the modem is provided by ISP. All you need to buy is the router and some Ethernet cables. FS.COM provides cat5e, cat6 and cat6a Ethernet cables with many color and length options. Snagless boot design prevents unwanted cable snags during installation and provides extra strain relief. Besides, custom service is also available. For more details, welcome to visit www.fs.com or contact us over sales@fs.com.

Source:http://www.fs.com/blog/how-to-build-a-home-network.html

S6100-ON vs Z9100-ON: Which Dell 100GbE Switch to Choose?

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Whether you recognize it or not, 100GbE is right here, right now. As the industry’s first multi-rate 100GbE 1U Ethernet switch, Dell’s Z9100-ON sets a high standard for the competition to follow. Soon afterwards Dell launched 2U 100GbE switches S6100-ON. These two Dell 100GbE switches support for a wide range of port speeds allows early adopters to move to 25GbE now and upgrade to 40GbE, 50GbE or 100GbE when the price is right. Which one did you deploy now? And why did you make the choice?

Dell Z9100-ON 100GbE Switches
The Dell Networking Z9100-ON is a 100GbE top-of rack (ToR) fixed switch purpose-built for applications in high-performance data center and computing environments. Z9100-ON 100GbE switch has 32 fixed 100GbE QSFP28 ports and a couple of 10GbE SFP+ ports to one side. This also allows for up to 64 ports of 50GbE, 32 ports of 40GbE, 128 ports of 25GbE or 128+2 ports of 10GbE switching all within the same module. Dell has thoughtfully provided these to allow you to connect legacy servers or switches without wasting a 100GbE port.

Dell 100GbE Switch Z9100-ON
Dell S6100-ON 100GbE Switches
Dell Networking S6100-ON Multi-rate Fabric Switch is a customizable fixed form factor 100GbE switch with 4 bays and 3 unique modules. It allows customers to mix and match modules delivering greater flexibility and choice than anything on the market today for this technology.
1) 16 ports of 40GbE. With 4 of these modules, customers can have up to 64ports of 40GbE in just 2RU!
2) 8 ports of QSFP28. This allows for up to 8 ports of 100GbE, 16 ports of 40 or 50GbE, or 32 ports of 10 or 25GbE switching all within the same module.
3) 4 ports of QSFP28 and 4 ports of CXP. The CXP ports allow for interconnects with legacy 100GbE in customer’s existing data centers as well as 4 ports of the newer/lower cost QSFP28.

Dell 100GbE Switch S6100-ON

S6100-ON vs Z9100-ON
If you want to build 100G network, both S6100-ON and Z9100-ON 100GbE switches can meet your requirement. Z9100-ON has fixed 100G QSFP28 ports and 10G SFP+ ports, and S6100-ON has fixed 100G QSFP28 ports, 100G CXP ports and 40G QSFP28 ports. Therefore, compared to Z9100-ON 100GbE switch, S6100-ON seems has more flexibility. And the S6100-ON price is higher than Z9100-ON. You can choose the right one for your specific requirements. To better power up your Dell S6100-ON or Z9100-ON 100GbE switches, you may need some good quality but cost-effectiive 100G optics and cables. FS.COM (Fiberstore) provides Dell QSFP28-100G-SR4 transceivers at 400 dollars and QSFP-100G-CWDM4 transceivers at 1350 dollars. And all these two transceiver modules are in stock now for same-day shipping. Besides the optics, Dell 100GbE QSFP28 to QSFP28 cables and 4x25GbE QSFP28 to SFP28 cables are also offered in Fiberstore for your option.

Related articles:

OpenFlow Switch: What Is It and How Does it Work?

Optics Solutions for FS.COM 100G Switches

Still Confused about CVR-X2-SFP10G Compatibility?

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The Cisco OneX Converter Module (model CVR-X2-SFP10G), also known as a converter module, is a hot-swappable input/output (I/O) device that slides into a 10-Gigabit Ethernet X2 slot on a switch. It converts the 10-Gigabit X2 interface into a single 10-Gigabit SFP+ interface. It is supported on many platforms using X2 interfaces. Which platforms are they? In fact, many people are confused about the CVR-X2-SFP10G compatibility. In this blog, I will give some knowledge about the compatibility for Cisco OneX CVR-X2-SFP10G Converter Module.

Cisco OneX CVR-X2-SFP10G Converter Module

CVR-X2-SFP10G Supported SFP+ Modules and Patch Cords

Not all SFP+ modules can be used for Cisco CVR-X2-SFP10G OneX converter module. Table below lists the SFP+ modules and twinax cables that available.

SFP+ Module Number Description
SFP-10G-SR Cisco 10GBASE-SR SFP-Plus transceiver module for MMF, 850nm wavelength
SFP-10G-LR Cisco 10GBASE-LR SFP-Plus transceiver module for SMF, 1310nm wavelength
SFP-H10GB-CU1M Twinax cable assembly, 1m, 30 AWG
SFP-H10GB-CU3M Twinax cable assembly, 3m, 30 AWG
SFP-H10GB-CU5M Twinax cable assembly, 5m, 24 AWG

Table below lists the fiber-optic cabling specifications for the SFP+ modules that you install in the converter module. Each port must match the wavelength specifications on the other end of the cable, and the cable must not exceed the stipulated cable length. The SFP modules using fiber-optic connections need fiber-optic cables with LC/PC or LC/UPC connectors.

SFP Module Wavelength Fiber Type Core Size (micron) Modal Bandwidth (MHz/km) Cable Distance
10GBASE-SR 850 MMF 62.5

62.5

50

50

50

160

200

400

500

2000

85 feet (26 m)

108 feet (33 m)

216 feet (66 m)

269 feet (82 m)

984 feet (300 m)

10GBASE-LR 1310 SMF 9 \ 32808 feet (10 km)

CVR-X2-SFP10G Supported Switch Series and Models

There are many switches that have X2 ports, but not all can be supported for CVR-X2-SFP10G OneX converter module. According to Cisco 10-Gigabit Ethernet Transceiver Modules Compatibility Matrix, the CVR-X2-SFP10G is supported on Catalyst 3100 Blade Switches, Nexus 7000 Series Switches, Catalyst 3560-E Series Switches, Catalyst 3750-E Series Switches, Catalyst 4500 Series Switches, Catalyst 4900 Series Switches, Cisco ME 4900 Series Switches, Catalyst 6500 Series Switches.

Switch Series Model
Catalyst 3100 Blade Switches WS-CBS3110X-S-I, WS-CBS3120X-S, WS-CBS3130X-S
Nexus 7000 Series N7K-M108X2-12L
Catalyst 3560-E Series WS-C3560E-24TD, WS-C3560E-24PD , WS-C3560E-48TD, WS-C3560E-48PD, WS-C3560E-48PDF, WS-C3560E-12D,WS-C3560E-12SD
Catalyst 3750-E Series WS-C3750E-24TD, WS-C3750E-24PD, WS-C3750E-48TD, WS-C3750E-48PD,WS-C3750E-48PDF
Catalyst 4500 Series WS-X4516-10GE, WS-X4013+10GE, WS-X45-SUP6-E, WS-X4606-X2-E, WS-X45-SUP6L-E
Catalyst 4900 Series WS-C4948-10GE,WS-C4928-10GE,WS-C4900M,WS-X4904-10GE,WS-X4908-10GE
ME 4900 Series ME-4924-10GE
Catalyst 6500 Series VS-S720-10G-3C,VS-S720-10G-3CXL,WS-X6708-10G-3C,WS-X6708-10G-3CXL,WS-X6716-10G-3C,WS-X6716-10G-3CXL,VS-S2T-10G,VS-S2T-10G-XL,WS-X6816-10G-2T,WS-X6816-10G-2TXL, WS-X6908-10G-2T,WS-X6908-10G-2TXL

Related Article:

Cisco SFP-10G-SR: All You Need to Know

A Comprehensively Understanding of Cisco 10G SFP+

Backbone Cabling vs Horizontal Cabling

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Computer networks require complicated and specific cabling, particularly in business or academic settings. The cables used in cabling the networks must be made from certain materials. Backbone cabling and horizontal cabling are two main cabling methods used in today’s structured cabling system and neither is dispensable. In order to meet different connection needs, cables used in backbone cabling and horizontal cabling also have many differences from each other. So what’s the difference between them? Knowledge of backbone cabling and horizontal cabling will be introduced in this article.

Structured Cabling System Basics

To understand backbone cabling and horizontal cabling, let’s understand the six subsystems of structured cabling firstly. These six subsystems are often found throughout a building and are connected together so that various types of data can be transmitted consistently and securely (as shown in the figure below).

Structured Cabling System

  • Entrance Facility: This room is where both public and private network service cables communicate with the outside world.
  • Equipment Room:  A room with equipment that serves the users inside the building.
  • Telecommunications Room: This room contains the telecommunications equipment that connects the backbone and horizontal cabling subsystems.
  • Backbone Cabling: A system of cabling that connects the entrance facilities, equipment rooms, and telecommunications rooms.
  • Horizontal Cabling: The system of cabling that connects telecommunications rooms to individual outlets or work areas on the floor.
  • Work Area Components: These connect end-user equipment to outlets of the horizontal cabling system.

Backbone Cabling

The backbone cabling is also called vertical cabling or wiring. It provides interconnection between telecommunication rooms, equipment rooms, and entrance facilities. These backbone cablings typically are done from floor to floor to floor. When setting up backbone cabling, several types of media can be used: unshielded twisted-pair (UTP) cable, shielded twisted-pair (STP) cable, patch cord, or coaxial cable. Equipment should be connected by cables of no more than 30 meters (98 feet).

Backbone Cabling

With the emerge of Gigabit Ethernet and 10 Gigabit Ethernet, fiber optic cable is the most appropriate choice for backbone cabling since they provide much higher bandwidth than traditional Cat5, Cat6 or even Cat7 twisted pair copper cables. Another advantage of fiber is that fibers can run much longer distance than copper cable, which makes them especially attractive for backbone cabling.

Horizontal Cabling

The horizontal cabling system extends from the work area’s telecommunications information outlet to the telecommunications room (TR) or telecommunications enclosure (TE). As shown in the figure below, horizontal cabling is usually installed in a star topology that connects each work area to the telecommunications room. It includes the telecommunications outlet, an optional consolidation point, horizontal cable, mechanical terminations and patch cords (or jumpers) located in the TR or TE.

Horizontal Cabling

Four-pair 100-ohm unshielded twisted-pair (UTP) cabling (Cat5 or Cat5e cabling) is usually recommended for new installations because it supports both voice and high-speed data transmission. To comply with EIA/TIA wiring standards, individual cables should be limited to 90 meters in length between the outlet in the work area and the patch panels in the telecommunications room. Patch cords for connecting the patch panel to hubs and switches in the telecommunications room should be no longer than 6 meters total distance. Cables connecting users’ computers to outlets should be limited to 3 meters in length.

Backbone Cabling  vs Horizontal Cabling

Although the same types of cables are used for both backbone and horizontal cabling, since backbone cabling typically passes through from floor to floor, the cables used for backbone cabling have the very different requirement from the horizontal cablings. Backbone cables must meet particular fire-rating specifications, typically OFNR (Optical Fiber Non-Conductive Riser) rated. If the backbone cable passes through plenum area (spaces in the building used for air return in air conditioning), the cable must be OFNP (Optical Fiber Non-conductive Plenum) rated. Besides, since backbone cables need to have enough strength to support its own weight, cable strength for backbone cables is also different from horizontal cables. And unlike horizontal cables, backbone cables must be secured correctly.

Conclusion

As two important parts of structured cabling, both backbone cabling and horizontal cabling play an irreplaceable role. And due to the different cabling environment, backbone cables and horizontal cables may have different specifications. FS.COM provides both Cat5, Cat6 or Cat7 UTP or STP copper cables and OFNR or OFNP multimode or single-mode fiber patch cables for backbone cabling and horizontal cabling. For more information about the backbone cabling and horizontal cabling solutions or other cabling solutions, please contact us via sales@fs.com.

Source:http://www.fs.com/blog/

Compatible Transceivers for Cisco Catalyst 4948E Switch

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Cisco Catalyst 4900 series switches were once the most widely deployed ToR (top-of-rack) switches in this industry. This post will introduce the detailed compatible transceivers information for Cisco Catalyst 4948E switch.

Cisco Catalyst 4948E

Port Information of Catalyst 4948E Switch
Cisco Catalyst 4948E switch is a one-rack-unit (1RU) fixed configuration network switch with 48 RJ45 ports of 10/100/1000M for downlink and 4 SFP/SFP+ ports of 1/10G for uplink on the front panel. The following picture shows the detailed port information of Cisco Catalyst 4948E switch.

Catalyst-4948E-F-ports-information

Downlink Connection for Cisco Catalyst 4948E Switch
The 48 ports on the front panel of Catalyst 4948E can support downlink of 10/100/1000M. The great advantage of these ports is that they can configure themselves to operate at the speed of the attached devices. If the attached devices do not support auto-negotiation, the speed and duplex parameters can be set explicitly. A network cable with a RJ-45 plug at both end can connect Cisco Catalyst 4948E switch to the downlink target devices.

Uplink Connection for Cisco Catalyst 4948E Switch
The four uplink SFP/SFP+ ports on Cisco Catalyst 4948E can support both copper and fiber optic transmission of 1G/10G by using different modules and cables. In addition, these ports can also support CWDM SFP transceivers and DWDM SFP transceivers. The following part will introduce the details about compatible transceivers for Cisco Catalyst 4948E switch.

Modules Connector & Cable
GLC-T (1000BASE-T) RJ45,Cat5
GLC-TE
GLC-SX-MM LC duplex, MMF
GLC-SX-MMD
GLC-LH-SM LC duplex, SMF
GLC-LH-SMD
GLC-EX-SMD
GLC-ZX-SM
GLC-ZX-SMD
CWDM SFP
DWDM SFP
GLC-BX-D LC simplex, SMF
GLC-BX-U
GLC-BX40-D-I
GLC-BX40-U-I
GLC-BX40-DA-I
GLC-BX80-U-I
GLC-BX80-D-I
Modules Connector & Cable
SFP-10G-LRM LC duplex, MMF
SFP-10G-SR
SFP-10G-SR-S
SFP-10G-LR LC duplex, SMF
SFP-10G-LR-S
SFP-10G-ER
SFP-10G-ER-S
SFP-10G-ZR
SFP-10G-ZR-S
DWDM SFP+
SFP-10G-BXD-I LC simplex, SMF
SFP-10G-BXU-I
SFP-10G-BX40D-I
SFP-10G-BX40U-I
SFP-H10GB-CU1M 10G SFP+ DAC Twinax Cable
SFP-H10GB-CU3M
SFP-H10GB-CU5M

Related Article: Cisco SFP-10G-SR: All You Need to Know

Cabling Solution for Upgrading to 40G and 100G Fiber

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Migrating from 10G (that uses two fibers in either a SC Duplex or a LC Duplex connector) to 40G and 100G fiber will require a lot more fibers and a different type of connector. The way that optical fiber cabling is deployed for 10G can facilitate an easier migration path to 40G and 100G fiber in the future. An effective migration strategy needs to provide a smooth transition to the higher Ethernet speeds with minimum disruption and without wholesale replacement of existing cabling and connectivity components.

10G use LC duplex cabling

Optical fiber cabling is commonly deployed for backbone cabling in data centers for switch to switch connections and also for horizontal cabling for switch to server and storage area network connections. The use of pre-terminated optical fiber cabling can facilitate the migration path to 40G and 100G fiber in the future. Figure below illustrates a pre-terminated cable assembly (MPO cassette) containing 24 OS2 single-mode fibers with two 12-fiber MPO connectors at both ends. This fiber cable assembly plugs into the back of a breakout cassette that splits the 24 fibers into 12 LC Duplex connectors at the front of the cassette.

MPO cassette has duplex lc connector and MTP connector

Four of these cassettes are mounted in a one rack unit (1U) patch panel to provide up to forty-eight 10G equipment connections using LC Duplex patch cords. The FS.COM FHD 1U fiber enclosure with four LC Duplex cassettes is illustrated in Figure below.

1U fiber enclosure with four LC Duplex cassettes

If upgrading from 10G to 40G, one or more of the LC duplex cassette(s) can be replaced with 12 port MPO adapters. The MPO adapters are designed to fit in the same opening as the cassettes. The Figure below illustrates the case where all four cassettes are replaced with four high density 12 port MPO adapters. This solution illustrates an upgrade path from 10G to 40G that does not require any additional space and reuses the same patch panels. The 12 LC duplex cassette(s) are replaced with 12 port MPO adapter(s) as needed. Additional 24-fiber cable assemblies (or any fiber counts in multiples of 12 fibers) are provided as needed for backbone or horizontal cabling.

1U fiber enclosure with four MPO adapter

How To Test Optical Loss with Light Source and Power Meter?

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In order to know how effectively your fiber optic cables are transmitting, you’ll need to test each one for optical loss. The term “optical loss” can also be called insertion loss, describes the difference between the amount of light sent into the transmitting end of a fiber optic cable, and the amount of light that successfully makes it to the cable’s receiving end. TIA-standards specify that you must measure optical loss using an optical power meter and the proper optical light source to certify an optical fiber cable. How to do that? This blog will tell you.

Introduction to Optical light source
A light source is a device that provides a continuous wave (CW) and stable source of energy for attenuation measurements. It includes a source, either an LED or laser, that is stabilized using an automatic gain control mechanism. LEDs are typically used for multimode fiber. On the other hand, lasers are used for singlemode fiber applications.

optical light source
The output of light from either an LED or laser source may also have the option of modulation (or chopping) at a given frequency. The power meter can then be set to detect this frequency. This method improves ambient light rejection. In this case, a 2 kHz modulated optical light source can be used with certain types of detectors to tone the fiber for fiber identification or for confirmation of continuity.

Introduction to power meter
The power meter is the standard tester in a typical fiber optic technician’s toolkit. It is an invaluable tool during installation and restoration. The power meter’s main function is to display the incident power on the photodiode.

Introduction to power meter
Transmitted and received optical power is only measured with an optical power meter. Optical loss must be measured with a optical light source. Connect one end of the fiber to the light source and the other end to the power meter. The light source sends a wavelength of light down the fiber. At the other end of the cable, the power meter reads that light, and determines the amount of signal loss.

Introduction to Testing Procedure

  • Connect the optical light source to the transmitting end of the test cable.
  • Connect the power meter to the receiving end of the test cable.
  • Turn on the source and select the wavelength you want for the loss test.
  • Turn on the meter, select the “dBm” or “dB” range and select the wavelength you want for the loss test.
  • Measure the power and loss at the meter.

Light Source and Power Meter

Cables with losses higher than 0.5 dB per end should be cleaned and retested. Dirt is always an issue. If any of the connectors are dirty, measurements will show higher loss and more variability. If the optical loss is still higher than 0.5 dB after cleaning, that means this cable is unqualified. Then you can discard it.

Related Article:

How to Test a Fiber Optic Transceiver?

Optical Power Meter (OPM): A Must for Fiber Cable Testing

What Are the Fiber Optic Cable Advantages and Disadvantages?

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What are the fiber optic cable advantages and disadvantages? An optical fiber or fiber optic cable is a flexible, transparent fiber made by drawing glass, which are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than wire cables. Whether should I use optical fiber cables in my network? Single mode fiber or multimode fiber? Don’t worry, read through this post to learn both fiber optic cable advantages and disadvantages and then make a right choice.

optical fiber

Fiber Optic Cable Advantages and Disadvantages

Advantages of Optical Fiber Cable
  • Bandwidth

Fiber optic cables have a much greater bandwidth than metal cables. The amount of information that can be transmitted per unit time of fiber over other transmission media is its most significant advantage.

  • Low Power Loss

An optical fiber offers low power loss, which allows for longer transmission distances. In comparison to copper, in a network, the longest recommended copper distance is 100m while with fiber, it is 2km.

  • Interference

Fiber optic cables are immune to electromagnetic interference. It can also be run in electrically noisy environments without concern as electrical noise will not affect fiber.

  • Size

In comparison to copper, a fiber optic cable has nearly 4.5 times as much capacity as the wire cable has and a cross sectional area that is 30 times less.

  • Weight

Fiber optic cables are much thinner and lighter than metal wires. They also occupy less space with cables of the same information capacity.  Lighter weight makes fiber easier to install.

  • Security

Optical fibers are difficult to tap. As they do not radiate electromagnetic energy, emissions cannot be intercepted. As physically tapping the fiber takes great skill to do undetected, fiber is the most secure medium available for carrying sensitive data.

  • Flexibility

An optical fiber has greater tensile strength than copper or steel fibers of the same diameter. It is flexible, bends easily and resists most corrosive elements that attack copper cable.

  • Cost

The raw materials for glass are plentiful, unlike copper. This means glass can be made more cheaply than copper.

Disadvantages of Optical Fiber Cable
  • Difficult to Splice

The optical fibers are difficult to splice, and there are loss of the light in the fiber due to scattering. They have limited physical arc of cables. If you bend them too much, they will break.

  • Expensive to Install

The optical fibers are more expensive to install, and they have to be installed by the specialists. They are not as robust as the wires. Special test equipment is often required to the optical fiber.

  • Highly Susceptible

The fiber optic cable is a small and compact cable, and it is highly susceptible to becoming cut or damaged during installation or construction activities. The fiber optic cables can provide tremendous data transmission capabilities. So, when the fiber optic cabling is chosen as the transmission medium, it is necessary to address restoration, backup and survivability.

  • Can’t Be Curved

The transmission on the optical fiber requires repeating at distance intervals. The fibers can be broken or have transmission losses when wrapped around curves of only a few centimeters radius.

Conclusion

Fiber optic cable has both advantages and disadvantages. However, in the long run, optical fiber will replace copper. In today’s network, fiber optic cable becomes more popular than before and is widely used. FS.COM, as a leading optics supplier, provides all kinds of optical fiber cables with high quality and low price for your option.

Related Article: What Are the Most Popular Fiber Optic Cable Types?

Related Article: What Kind of Fiber Patch Cord Should I Choose?

100G Optical Transceivers Links: PSM4 vs CWDM4

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In the past few years, 100G optical transceivers are become more popular and widely used than before. The most common 100G optical transceivers we use today are CFP, CFP2, CFP4 and QSFP28, especially the QSFP28. Besides 100G optical transceivers links (-SR10, SR4, -LR4) defined by IEEE standard, Multi-Source Agreement (MSA) also defines two 100G optical transceivers links: PSM4 and CWDM4. Both architectures take the 100GE signal and carry it over 4 separate channels. So, what’s the difference between them? PSM4 vs CWDM4–difference between them will be introduced in this blog.

PSM4
The 100G PSM4 Specification defines requirements for a point-to-point 100 Gb/s link over eight single mode fibers (4 transmit and 4 receive) up to at least 500 m, each transmitting at 25Gbps. Four identical and independent lanes are used for each signal direction (as shown in figure below). Therefore, two transceivers communicate usually over 8-fiber MTP/MPO single mode patch cords. PSM4 is limited to 500 m, and it is usually used in 100G QSFP28 optical transceivers.

100G Optical Transceivers Links PSM4

CWDM4
Similar to PSM4, CWDM4 also uses 4 x 25 Gbps to achieve 100 Gbps. But unlike it, CWDM4 uses an optical multiplexer and de-multiplexer to reduce the number of fibers to 2 (as shown in figure below). Therefore, we only need to use a duplex single mode fibers to connect two 100G CWDM4 optical transceivers modules. CWDM4 is limited to 2 km. At present, CWDM4 links are used in both 100G CFP4 or the QSFP28 optical transceivers.

100G Optical Transceivers Links CWDM4

100G Optical Transceivers Links: PSM4 vs CWDM4
A summary table comparing the key differences between the two 100G transceivers is shown below. From an optical transceiver module structure viewpoint, PSM4 can be more cost effective because it uses a single uncooled CW laser which splits its output power into four integrated silicon modulators. However, from an infrastructure viewpoint, this transceiver would be more expensive when the link distance is long, mainly due to the fact that it uses 8 optical single-mode-fibers while CWDM4 uses only 2 optical single-mode-fibers.

100G Optical Transceivers Links PSM4 vs CWDM4
When considering the above two factors, a total cost comparison can be qualitatively shown in the figure below. As can be seen in the figure, PSM4 starts with a lower cost due to its lower transceiver cost, but as the link distance increases, its total cost climbs up very fast due to the fact that it uses 8 optical fibers.

100G links PSM4 vs CWDM4

Conclusion
Different companies have different opinions on what the link distance is at the crossing point, and what the transceiver cost difference is at zero distance. But based on the specifications of PSM4 MSA, the technology has to be limited to 500 meters, which can actually cover the majority of today’s data center needs. FS.COM provides both 100G PSM4 QSFP28 ($ 750.00) and 100G CWDM4 QSFP28 ($ 1350.00) optical transceivers for your options.

Related Article: https://www.cables-solutions.com/100g-qsfp28-pam4-coherent-cfp.html

Do You Use QSFP+ Direct-Attach Twinax Copper Cable?

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To achieve a 40G network connection, we usually use QSFP+ transceiver modules and MTP patch cords, which can help transmit 150 m to 40 km. But, if we only need to connect within 10 m, we can use QSFP+ direct-attach twinax copper cables. It’s a high-speed, cost-effective alternative to QSFP+ fiber optics. What’s QSFP+ direct-attach copper (DAC)? Whether should I use it? This blog will introduce the knowledge of QSFP+ DAC to you.

What Is QSFP+ Direct-Attach Twinax Copper Cable?
QSFP+ DAC is also called QSFP+ to QSFP+ cable. It has a QSFP+ module at one end and another QSFP+ module at the other end, and uses integrated duplex serial data links for bidirectional communication. Used to connect the 40 Gbps QSFP+ port of a switch at one end to another QSFP+ port of a switch at the other end, it can provide high quality of 40G end-to-end connection. Usually, maximum transmission distance of QSFP+ DAC is 10 m, which makes these cables are suitable for in-rack connections between servers and Top-of-Rack (ToR) switches. Besides, since its price ($30-$200) is much lower than QSFP+ optics, it’s a more cost-effective option to connect within racks and across adjacent racks.

QSFP+ DAC

Passive vs Active QSFP+ DAC
QSFP+ direct-attach twinax copper cable comes in either an active or passive twinax (twinaxial) and connects directly into a QSFP+ housing. An active twinax cable has active electronic components in the QSFP+ housing to improve the signal quality. A passive twinax cable is mainly just a straight “wire” and contains few components. Generally, twinax cables shorter than 5 meters are passive and those longer than 5 meters are active, but this may vary from vendor to vendor. QSFP+ direct-attach copper is a popular choice for 40G Ethernet reaches up to 10 m due to low latency and low cost.

Popular QSFP+ Cable Overview
At present, major QSFP+ DAC vendors are Brocade, Arista and Cisco. We can use QSFP+ DAC in their hardware with QSFP+ interfaces. Although the transmission distance of QSFP+ DAC can reach 10 m, the most common types we use are 1 m, 3 m, and 5m. In the market, popular QSFP+ DAC includes Brocade 1m(40G-QSFP-C-0101) , 3m(40G-QSFP-C-0301) and 5m(40G-QSFP-C-0501) passive QSFP+ twinax copper, Arista 1m(CAB-Q-Q-1M) and 3m(CAB-Q-Q-3M) passive QSFP+ twinax copper, and Cisco 1m(QSFP-H40G-CU1M) and 3m(QSFP-H40G-CU3M) passive QSFP+ twinax copper.

Brocade,Arista and Cisco DAC

Conclusion
40 Gbps Direct-Attached QSFP+ to QSFP+ Copper Cables (1 m, 3 m, 5 m) are optimized to fully leverage 40 Gigabit Ethernet (GbE) switches and routers. FS.COM provides a wide range of QSFP+ cable assembly options for your network connection, which satisfies the need for ultra-thin, light-weight, highly flexible cabling solutions for use in high density intra-rack applications.

Related Article: 40G QSFP+ Direct Attach Copper Cabling