Will QSFP28 be a better way to 100G?
The Quad Small Form-factor Pluggable (QSFP) is a compact, hot-pluggable transceiver used for data communications applications. The form factor and electrical interface are specified by a multi-source agreement (MSA) under the auspices of the Small Form Factor Committee. It interfaces networking hardware to a fiber optic cable or active or passive electrical copper connection. It is an industry format jointly developed and supported by many network component vendors, allowing data rates from 4x10 Gbit/s.The format specification is evolving to enable higher data rates; as of May 2013, highest possible rate is 4x28 Gbit/s (also known as QSFP28).
4 x 28 Gbit/s QSFP+ (QSFP28)
The QSFP28 standard is designed to carry 100 Gigabit Ethernet, EDR InfiniBand or 32G Fibre Channel. This transceiver type is also used with direct-attach breakout cables to adapt a single 100GbE port to four independent 25 gigabit ethernet ports (QSFP28-to-4x-SFP28) Sometimes this transceiver type is also referred to as "QSFP100" or "100G QSFP" for sake of simplicity.
The 100G QSFP28 transceiver modules are designed for use in 100 Gigabit Ethernet, 128GFC and 4x28G OTN links over multimode fiber. They are compliant with the QSFP28 MSA, 128GFC, IEEE 802.3bm 100GBASE-SR4 and CAUI-4. Digital diagnostics functions are available via the I2C interface as specified by the QSFP28 MSA.
An optical transceiver form factor is specified by a multisource agreement (MSA). An MSA is an agreement between multiple manufacturers to make optical transceivers that can plug into switches.
QSFP28 module uses four lanes for 100G optical signal transmitting like 40G QSFP+. However, each lane of QSFP28 can transmit 25G optical signal. To fit the various requirements in practical applications, IEEE and MSA standards that support different transmission distances and fiber types are being published.
100Gbase SR4 QSFP28 module uses eight multimode fibers for 100G dual-way transmission over 850nm. It can support a transmission distance up to 70m over OM3 and 100m OM4 with a MTP interface. 12-fiber MTP OM3/OM4 trunk cables are suggested to be used with QSFP-100G-SR4 modules. 100Gbase-SR4 QSFP28 is the most popular QSFP28 module according to research.
It focuses on longer transmission distance over single-mode fiber. 100Gbase-LR4 QSFP28 has a duplex LC interface and uses WDM technologies to achieve 100G dual-way transmission over four different wavelengths around 1310nm. It can support distances up to 10km.
The 100G-QSFP-LR4 module can support 10km, which is too much for a lot of single-mode applications. It would be uneconomical to buy a 10km module for just 1km or 2km application. MSA has published two 100G standards — 100Gbase-PSM4 and 100Gbase-CWDM4, which can help to decrease the cost of 100G deployment.
100Gbase-PSM4 QSFP28 module has a MTP interface working on wavelength of 1310nm for 100G transmission over single-mode fibers. It can support transmission distance up to 500 meters. 100Gbase-PSM4 QSFP28 module is much cheaper than 100Gbase-LR4 QSFP28 module. And 500 meter’s transmission distance can cover a wide range of applications.
For longer transmission distance, 100Gbase-CWDM4 QSFP28 is suggested, which supports a distance up to 2km over single-mode fiber optic cable. 100Gbase-CWDM4 standard is published by MSA, which is a more cost-effective solution for a wide range of applications compared with 100Gbase-LR4. This module uses CWDM technologies to transmit the 100G optical signal via a duplex LC interface over wavelengths near 1310nm.
100G QSFP28 DAC
100G QSFP28 family also includes a series of direct attach cables. There are mainly two types of QSFP28 DAC, which are QSFP28 to QSFP28 DAC and QSFP28 to SFP28 DAC. These QSFP28 DACs are cost-effective solution for 100G transmission less than 5 meters.
What is the Low Smoke Zero Halogen Cable?
Cables are predominant components in tree structure of a digital data center, ensuring the flow of vital information from one active device to another. In order to have products that have fire resistance properties in data center, it is important to focus on each LAN or WAN component to see the standard fire compliant standards that are present in such a catastrophic scenario.
A PVC cable (made of polyvinyl chloride) has a jacket that gives off heavy black smoke, hydrochloric acid, and other toxic gases when it burns. Low Smoke Zero Halogen (LSZH) cable has a flame-resistant jacket that doesn't emit toxic fumes even if it burns.
On the cable industry market, there are two standards that are predominant for non-PVC cables in the fire conditions:
Historically, the European product safety standards have focused on cable designs that exclude halogens in their designs. The IEC 60332-1 governs the flame retardant
grade specifications for cables for LANs, WANs and other networking products. IEC 60332-1 applies to the majority of medium and large-scale installations in Europe. It requires LSZH jackets on cables installed near places where people congregate or anywhere there is exposed wire.
U.S. standards, on the other hand, have focused on the product’s fire resistance properties and its resistance to propagation of flame during fire conditions.
The current cost-effective compound technology available for the industrial wire and cable market forces engineers to choose either excellent flame performance or halogen-free, low-smoke performance without sacrificing electrical performance.
Wire and cable insulations are generally broken down into two distinct types, thermoplastic and thermoset.
The primary difference being that a thermoplastic material will melt when exposed to high heat or fire conditions, while a thermoset material will not melt when exposed to heat, will better resist softening and degrading, and will turn to a char under high heat or fire conditions.
As thermoset materials inherently provide better emergency performance at elevated temperatures, electrical overload conditions, and better flame propagation resistance than a thermoplastic material, they are generally preferred in industrial applications, as the conductor will have a greater propensity to see these types of operating temperatures during normal operation.
The properties of a thermosetting compound are created by an irreversible chemical reaction during processing which causes the molecules to link (cross-link), thereby “strengthening” their molecular structure. While these cross-linking properties are extremely beneficial to cable performance, they also make the development of thermosetting compounds with comparable properties to thermoplastic materials more difficult and have historically presented a greater challenge to the industry.
European standards tend to focus on cable designs generating low-smoke and containing zero-halogens (LSZH) and specific electrical requirements, while the North American standards primarily focus on a combination of fire retardancy and specific electrical performance, with a high degree of emphasis on wet electrical qualifications.
The term “low-smoke, zero-halogen” describes two distinct properties of a cable compound. The term “low- smoke” describes the amount of smoke which a compound emits when burned, while “zero-halogen” describes the amount of halogens used to make the compound. Designated halogen-free cables, hand, do not produce a dangerous gas/acid combination when exposed to flame.
In Data Center cabling and specially in patching, we may find the Cat5e UTP LSZH cable that is performance optimized with 4 balanced twisted pairs on 24 AWG insulated solid bare copper conductors. SCP Cat5e UTP LSZH cables are constructed to create a round and flexible cable for easy pulling and stripping of the LSZH jacket.
How are cables tested or what are the main functional tests that have to be passed by the LSZH cables?
Certified and listed by a nationally recognized independent testing laboratory Halogen content measurement. The thermoset insulations are rated for use at 90°C wet and dry conditions.
News for Friday 10 July, 2020