Quad (4-channel) Small Form-factor Pluggable Optics Transceiver, also known as QSFP+, is an acronym for Quad (4-channel) Small Form-factor User Space Optics Transceiver. It's a hot-pluggable, lightweight fiber optical transceiver for 40 Gigabit Ethernet (40GbE) transmitting data. They are commonly used in data centers, 40G Ethernet, Fiber Channel, and other networking protocols, and are built according to QSFP+ Multi-source arrangement and IEEE802.3ab.
It connects a network system (such as a switch, modem, or media converter) to a fiber optic or copper cable. It is an industry-standard format specified by the Small Form Factor Committee. Finisar, Opnext, and Sumitomo/ ExceLight were among the founding members of the CFP MSA, which was officially launched at OFC/NFOEC 2009 in March. The format specification is expanding to accommodate higher data rates. As of May 2013, the maximum supported rate is 4x28Gbps (112Gbps), which will support 100GE as specified in the SFF-8665 document (commonly known as QSFP28).
High-density 40G networking solutions for powerful processing networks and new data centers are provided by this parallel and hot-swappable fiber optical module. It has four independent receive and transmit analog networks that can link to another 40G QSFP+ transceiver or four different 10 Gigabit SFP+ transceivers. In a nutshell, QSFP+ modules link the system's electrical control circuitry to optical public networks.
40G QSFP+ Interface
There is a range of 40G transceivers on the market right now. 40G QSFP+ optics, on the other hand, adhere to the QSFP MSA specification, which states that 40G QSFP+ connectors should be either 12-fiber MPO or duplex LC.
Simply placed, 40G QSFP+ transceivers with an LC protocol are used to send information over long distances over single-mode fiber (SMF), whereas transceivers with an MPO interface (except for 40GBase-PLR4 and 40GBase-PLRL4) are used to transmit small amounts of data over multimode fiber (MMF). Furthermore, MPO interfaced QSFP+ transceivers could be used in 4x10G networking using a crossover cable, while LC interfaced QSFP+ transceivers cannot be separated into 4x10G since they use four wavelengths on a single pair of SMF.
Data is sent over to laser drivers through four channels of 10G serial data streams of different frequencies in the LC interface. The DML or wavelength-controlled lasers are controlled by the same laser drivers. The DML outputs are then electrically multiplexed to a single-mode fiber via a generic LC connector, resulting in a 40G transmission. The 40G signal is demultiplexed into four independent 10G streams at varying wavelengths on the receiver side. Each wavelength of light is collected by a diode, intensified by a TIA, and then output as electric data.
Starting from the transmission side, as it transmutes parallel electrical input signals into parallel optical signals through a laser array, the operating concept of a 40G QSFP+ transceiver with an MPO interface can be demonstrated. The optical signals are then transmitted via the MMF ribbon, which is MPO-terminated. The receiver, on the other hand, uses a photodetector array to convert parallel optical control signals into parallel output electrical signals.
Types of 40G QSFP+ Modules
Because of the massive increase in data traffic, many data centers are outfitted with 10G and 40G Ethernet switches to facilitate 10G to 40G conversion. 40G switches allow a 40G port to be configured as a single port or to be split into four separate ports. We can choose 40G QSFP+ transceivers that can break out as 4x10G connections for fast 10G/40G conversion. The 40G QSFP+ price range is affordable and equally industry-efficient.
40G QSFP+ SR4
40GBase-SR4 is the most commonly used and popular 40G transceiver for short-distance transmission, primarily over OM3 and OM4 multimode fibers with connection lengths between 100m and 150m. It's a parallel fiber optic transceiver with an MPO interface and a 4x10G transmission pattern. With the support of four 10G SFP+ lanes in one module, the 40GBase-SR4 can send and receive 40G signals at the same time. This form of transceivers is often used in data centers to link two switches using 12 lane ribbon cables.
40G QSFP+ LR4
The 40GBase-SR4 is used for short-range data transmission, while the 40GBase-LR4 is used for long-range data transmission. While they both use multi-lane technology, the LR4 differs in its multiplexes with four different lanes on two different channels of fiber strand to transmit and receive signals. Rather than having a single fiber strand for each lane for data transmission, it uses different lanes to serve the purpose. This transceiver style uses a single-mode fiber cable with duplex LC connectors to support connection lengths of up to 10 kilometers.
40G QSFP+ CSR4
The 40G QSFP+ CSR4 module works in the same way as the 40GBase-SR4 module such that they all have an MPO interface. The CSR4, on the other hand, can be considered an improvement to the SR4 because it can accommodate longer data transfer. OM3 can go up to 300m and OM4 can go up to 400m.
There are other types of 40G QSFP+ Transceiver modules such as 40G QSFP+ LR4L and 40G QSFP+ ER4 that can be used depending on your organizational needs.