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FAQs for QSFP28 Optical Transceivers

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. 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.

What does QSFP28 stand for?
QSFP28 is Abrreivated from Quad Small Form-Factor Pluggable 28. It is the third generation of the QSFP interconnect systems designed for 25/100G performance per the IEEE 802.3bj specification (100GBASE-CR4).

What is the maximum supported distance for 100G Transceivers and Cables?
The maximum currently supported distance for 100G is 80km with DWDM QSFP. For non-DWDM optics, QSFP-100G-ERL4 supports up to 40km and QSFP-100G-LR4 supports up to 10km. Additional optics may be released in the future to support longer distances.

What is the difference between QSFP28 and 100G QSFP?
They are the same. The “QSFP” form factor was originally defined for <10G speeds. When it was adopted for 40G, the name became QSFP+ to denote the higher aggregate performance. The same “QSFP” form factor was later adopted for 100G but the electrical interface had to be upgraded to handle 25Gbps/lane. The electrical interface for 100G can handle up to 28Gbps, hence the engineering and industry name is QSFP28. Arista refers to the 100G form factor as “100G QSFP” to avoid any confusion.

Are TARLUZ 100G Transceivers interoperable with other 100G transceivers available in the industry?
Yes, as long as the non-TARLUZ 100G transceivers meet the associated industry standard specifications, TARLUZ 100G transceivers are fully interoperable.

Where can customers buy splitter cables for 4x25G connectivity?
TARLUZ offers the MTP-LC or MPO-LC multimode fiber breakout cables available and are supplying these in volumes to customers for 40G to 4x10G. The same fiber splitter cable can be used for 100G to 4x25G.

Do you offer custom EEPROM programming?
Yes, upon request. Cables with custom EEPROMs will be supplied under a different part number.

What cable jacket color is available for the QSFP28 AOC and QSFP28 DAC?
Standard jacket color is black. Red, white and blue jackets are available on special order.

Do these products support the 25G per lane data rate and for what standards?
Yes, per SFF-8636, SFF-8661, SFF-8665, SFF-8679 and IEEE 802.3bj, these cables support 25/100G Ethernet.

Where are these cable assemblies used?
These are “point-to-point” cables that are used to directly connect two pieces of active network equipment like switch-to-switch or switch-to-server applications. They are most commonly used in data centers for ToR (top of rack) or MoR (middle of rack) aka leaf-spine applications that require increased bandwidth.

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