Cabling in the Data Center

Passive, Active, Copper & Fiber | Cost, On-board & Cable-based Equalization | Questions to ask your data center cable supplier

Cabling is an increasingly important topic in the data center. This focus is growing with the proliferation of 10 Gb/s and 40 Gb/s cables in volume today, with 100 Gb/s cables already starting deployments, and with both intra-rack and inter-rack applications.

Data Center Cabling: Passive, Active, Copper and Fiber Considerations

Passive cabling provides a direct electrical connection between corresponding cable ends. Active cables provide the same effect but, by embedding optics and/or electronics within the connectors, can overcome some of the limitations of passive cables. While passive cables are always copper-based, active cables can use either copper wire or fiber optics to provide the link between the cable ends.Leading types of passive and active cables for the data center

As a data center manager or planner, why do you care about these distinctions? And what are the significant strengths and weaknesses of each?

This table highlights five key attributes and characterizes each of these cable types. After the table you’ll find more explanation of each of these attributes.Key attributes of cable types

Cable span: Traditional passive copper cables are primarily deployed today to connect equipment within a single rack (intra-rack connections). Depending on the cable type and application, they are typically limited in distance to 7-10 meters. By contrast, an active cable has electronics and possibly optics embedded within the connectors on each end, allowing the cable to overcome most physical distance limitations. In the case of active copper cabling, electronics in each end of the cable can boost, equalize and otherwise treat the signals going onto the copper wire, and the electronics on the other end then restores them to original levels, allowing cable distances suitable for use within racks and between racks (inter-rack). In an active optical cable, the connectors translate electrical signals to optical ones, and vice-versa, allowing longer distances, and providing even greater data center configuration flexibility. With active optical cables, the same cable technology can serve both intra- and inter-rack applications.

Cable attributes: For equivalent data rates, optical cable is thinner and lighter than copper wire, and it does not need to be shielded. For these reasons, an optical cable is often lighter in weight and less bulky, and has a smaller bend radius, than the equivalent copper cable, especially with longer cables. These advantages of fiber provide more data center configuration flexibility.

Optical cables vs copper cables: Thickness and weight

Cooling and airflow considerations:  The physical volume of large numbers of cables can have significant effects on the cooling efficiency and lifetime of the connected equipment, as well as the cooling requirements and power consumption of racks and the entire data center facility. Thin, lightweight optical cables have a clear advantage in this regard.

Power consumption: Today, cables consume relatively little power when compared to processors and other components, or to fans and cooling. But as those systems are becoming more energy efficient, the focus on cable energy consumption is growing. As a rule, the amount of energy dissipated, and the amount of power required to transmit over a passive copper cable is directly related to its length. Active cables, both copper and optical, tend to have fixed power consumption without regard to their length. Finally, the superiority of optics for longer cable distances is well known.

Electromagnetic interference (EMI): Electromagnetic radiation from copper cables, whether passive or active, is highly dependent on the quality standards of the manufacturer, and with copper cables both the connectors and the conductors can emit EMI. The low cost of third-party passive copper cables is often attractive, but their EMI characteristics can be very unpredictable. With active optical cabling, EMI can come only from the components within the connectors on the cable ends, since the cable itself emits no electromagnetic radiation. As a general rule, these optical components are more carefully designed and shielded that their copper cable equivalents. As a result, optical cables tend to be superior from an EMI perspective.

Other issues to consider

Here are some other considerations you may want to keep in mind when making data center cable decisions:

Cost: The price of copper can be volatile (see chart), but the cost of fiber cables is falling, as manufacturing volumes increase and the technology continues to improve. Some analyses show that, when lifetime costs like deployment, cooling and energy consumption are considered, fiber solutions are more cost-effective. Over the long term, copper prices, ignoring the volatility, are rising, as evidenced by the growing number of thefts of copper wire.Historical copper prices

On-board vs. cable-based equalization: There is discussion of the merits of performing signal processing and equalization within cables, as opposed to doing it inside the ports being connected. As noted earlier, cable of different lengths may have different operating characteristics. As a result, performing these functions within the cable has the advantage of insulating the connected devices from any distance-related configuration or performance issues.

Get to know the 100GBASE QSFP28

Description

Gigalight GQS-MP101-XXXCL is a Four-Channel, Pluggable, Parallel, Fiber-Optic QSFP+ SR4 for 100 or 40 Gigabit Ethernet , Infiniband FDR/EDR and 32GFC Applications. This transceiver is a high performance module for short-range multi-lane data communication and interconnect applications. It integrates four data lanes in each direction with 112.2 Gbps bandwidth. Each lane can operate at 28.05Gbps up to 70 m using OM3 fiber or 100 m using OM4 fiber. These modules are designed to operate over multimode fiber systems using a nominal wavelength of 850nm. The electrical interface uses a 38 contact edge type connector. The optical interface uses an 12 fiber MTP (MPO) connector. This module incorporates Gigalight Technologies proven circuit and VCSEL technology to provide reliable long life, high performance, and consistent service.

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Features (Low Power Version)

▪ Bandwidth density of 100 Gbps bi-directional
▪ Transmission data rate up to 25.8Gbps per channel
▪ 4 channels 850nm 25G VCSEL array
▪ 4 channels 25G PIN photo detector array
▪ Internal CDR circuits on both receiver and transmitter channels
▪ Hot Pluggable QSFP28 form factor
▪ Maximum link length of 70m on OM3 Multimode Fiber (MMF) and 100m on OM4 MMF
▪ Operating case temperature 0°C to +70°C
▪ 3.3V power supply voltage
▪ Low power consumption <2.5W
▪ RoHS 6 compliant(lead free)

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Applications

▪ IEEE 802.3bm 100GBASE SR4
▪ InfiniBand EDR
▪ Datacom/Telecom switch & router connections
▪ Data Aggregation and Backplane Applications
▪ Proprietary Protocol and Density Applications

40G QSFP+ to 4x 10G SFP Breakout AOC

Description

Gigalight QSFP to 4x SFP+ breakout Active Optical Cable offers IT professionals a cost-effective interconnect solution for merging 40G QSFP and 10G SFP+ enabled host adapters, switches and servers. For typical applications, users can install this splitter Active Optical cable between an available QSFP port on their 40Gbps rated switch and feed up to four upstream 10GbE-SFP+ enabled switches. Each QSFP-SFP+ splitter Active Optical cable features a single QSFP connector (SFF-8436) rated for 40Gbps on one end and (4) SFP+ connectors (SFF-8431), each rated for 10-Gb/s, on the other.

Features

Electrical interface compliant to QSFP+ connector (SFF-8436) and SFP+ connectors (SFF-8431)

Hot Pluggable

850nm VCSEL transmitter, PIN photo-detector receiver

Up to 100m on OM3 MMF

Operating case temperature: 0 to 70℃

All-metal housing for superior EMI performance

RoHS compliant (lead free)

Applications 

◇ 40 Gigabit Ethernet

◇ Fibre Channel Applications

◇ InfiniBand QDR, SDR, DDR

◇ High-performance computing clusters

◇ Servers, switches, storage and host card adapters 

Further concerns could refer to jason@gigalight.com

Get to know the DataCom 40G QSFP+ AOC

40G QSFP+ are still the mainstream optical transceivers being used in communication and networking, and playing an important role to drive the sales of 10-, 40- and 100-Gbps optical transceivers for enterprise and data center applications, even if the 100G optical module has been released and used more and more. 40G QSFP+ transceivers demand growth over SMF is primarily a result of large shipments to Internet content providers like Google, Microsoft and Baidu. So we'd like to introduce the DataCom QSFP+ active optical cables (AOC) for enterprise and data center networks.

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Description

QSFP active optic cables has a high performance, low power consumption, long reach interconnect solution supporting 40G Ethernet, fiber channel and PCIe. It is compliant with the QSFP MSA and IEEE P802.3ba 40GBASE-SR4. Gigalight QSFP AOC is an assembly of 4 full-duplex lanes, where each lane is capable of transmitting data at rates up to 10Gb/s, providing an aggregated rate of 40Gb/s.

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Features 

▪ Full duplex 4 channel 850nm parallel active optical cable

▪ Transmission data rate up to 10.3Gbit/s per channel

▪ SFF-8436 QSFP+ compliant

▪ Hot pluggable electrical interface

▪ Differential AC-coupled high speed data interface

▪ 4 channels 850nm VCSEL array

▪ 4 channels PIN photo detector array

▪ Maximum link length of 300m on OM3 Multimode Fiber (MMF)and 400m on OM4 MMF

▪ Low power consumption <1.5W

▪ Operating case temperature 0°C to +70°C

▪ 3.3V power supply voltage

▪ RoHS 6 compliant

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Applications

▪ Infiniband transmission at 4ch SDR, DDR and QDR

▪ 40GBASE-SR4 40G Ethernet

▪ Data Centers 

Further details could be available on jason@gigalight.com.

Data Interconnection: 40G QSFP+ to 8x LC Connector Breakout AOC

Gigalight QSFP+ to 8 x LC Connector Breakout Optical Cable are a high performance, low power consumption, long reach interconnect solution supporting 40G Ethernet, fiber channel and PCIe. It is compliant with the QSFP MSA and IEEE P802.3ba 40GBASE-SR4. Gigalight QSFP+ Breakout Cable is an assembly of 4 full-duplex lanes, where each lane is capable of transmitting data at rates up to 10Gb/s, providing an aggregated rate of 40Gb/s. QSFP+ Breakout Cable are suitable for short distances and offer a highly cost-effective way to connect within racks and across adjacent racks. These breakout cables connect to a 40G QSFP+ port of a switch on one end and to four 10G SFP+ Transceivers of a switch on the other end.

Features 

Full duplex 4 channel 850nm parallel active optical cable; 

Transmission data rate up to 10.3Gbit/s per channe;l 

SFF-8436 QSFP+ compliant; 

Hot pluggable electrical interface; 

Differential AC-coupled high speed data interface;

4 channels 850nm VCSEL array;

4 channels PIN photo detector array;

Maximum link length of 300m on OM3 Multimode Fiber (MMF)and 400m on OM4 MMF;

Low power consumption;

Housing isolated from connector ground;

Operating case temperature 0°C to +70°C;

3.3V power supply voltage;

RoHS 6 compliant.

Applications 

#Infiniband transmission at 4ch SDR, DDR and QDR 

#40GBASE-SR4 40G Ethernet 

#Data Centers

Further details could be available via jason@gigalight.com.