Thanks for your question. The mainly difference is the 40G LX4 QSFP+ transmission distance 2km & 40G LR4 QSFP+ transmission distance 10km. For more detailed information, please check the datasheet of JNP-QSFP-40G-LX4 #36175 and QSFP-40GE-LR4 #36114 accordingly. By FS.COM on September 20, 2017

As for customized transceivers, FS.COM offers regular custom choices such as compatibility, transmission distance, operating temperature, label pattern, label colors and etc. What's more, FS.COM welcomes any inquiry for customized products and solutions for all need and specifications. By FS.COM on July 15, 2017

Besides the price advantage we have compared to branded transceivers, FS.COM compatible transceivers also maintain the same performance and reliability. To satisfy our customers' needs of high performance, all of our transceivers are tested multiple times in mainstream original brand switches in our test center before shipped out. By FS.COM on June 07, 2017

On one hand, the FS.COM 40G QSFP+ transceivers with LC interface are used for long-distance transmission over single mode fiber, and those with MTP/MPO interface are utilized for short distance transmission over multimode fiber. On the other hand, for the FS.COM 40G QSFP+ transceivers with LC interface, they cannot be split into 4x10G as they use 4 wavelengths on a pair of single-mode fibers and do not lend themselves to “splitting” into 4 pairs without substantial complexity to split out the wavelengths. For the FS,COM 40G QSFP+ transceivers with MTP/MPO interface, they can be used in 4x10G connectivity via an external 12-fiber parallel to 2-fiber duplex breakout cable, which connects the 40G transceiver to four 10G optical interfaces. By FS.COM on June 05, 2017

FS.COM has been maintaining adequate stock level of the 40GBASE-LX4 QSFP+ transceivers in U.S. warehouse, EU warehouse and CN warehouse. As long as the products you order are all in stock, we will ship them out the same day you place your order. As for some specific products or products that have a short stock, we will keep you informed ahead of time before you place your order. By FS.COM on June 03, 2017

The FS.COM 40GBASE-LX4 QSFP+ transceivers enable data centers running at 10G today to seamlessly upgrade to 40G without having to re-design or modify the cable infrastructure, which allows our customers to migrate their existing 10G infrastructure to 40G at zero cost of fiber and to expand the infrastructure with low capital investment. They also offer a transition path for customer planning migrations to single-mode fiber in data centers with a single transceiver that bridges the gap between multi-mode and single-mode optics. By FS.COM on June 21, 2017

Dust and contamination can accumulate on transceiver's connectors and cause problems such as reducing the optic launch power. To ensure better connection, FS.COM strongly recommends cleaning both connectors each time you disconnect and reconnect them. FS.COM High Quality One-Push Fiber Optic Pen Cleaner for 1.25mm LC/MU Connector is the best cleaning choice for 40GBASE-LX4 QSFP+ transceivers. By FS.COM on May 18, 2017

The FS.COM 40GBASE-LX4 QSFP+ transceivers use both duplex single mode fiber patch cables and multimode fiber patch cables with LC connectors. By FS.COM on May 10, 2017

No. Network equipment manufacturers do not require that you use only name-brand optics. In fact, when a product fault or defect occurs in the network, and the fault or defect is not attributable to the use of third-party optics, they will continue to provide support for the affected product under warranty or covered by their support program. By FS.COM on April 12, 2017

The FS.COM 40GBASE-LX4 QSFP+ transceivers support up to 2km over single mode fiber and up to 150m on OM3 and OM4 multimode fibers. By FS.COM on March 17, 2017