In data centres, a fibre optic connector/optical interface called MPO is often used. For example, the optical interface of the 400G DR4 optical module mentioned in our previous article is MPO. MPO optical connectors can be applied to multimode fibres as well as used as connectors for single-mode fibres.
In data centres, the optical modules that are commonly used with MPO optical interfaces are as follows:
- MMF OM3/OM4
- 20 (for MMF OM3/OM4)
- 16 (for MMF OM3/OM4)
- 8 (for both MMF OM3/OM4 and SMF)
- For 20 cores: MPO 2x12
- For 16 cores: MPO 1x16 APC and MPO 2x12
- For 8 cores (MMF): MPO 1x12
- For 8 cores (SMF): MPO 1x12 APC
- SR4/eSR4 at 4x10Gbps (for 8 cores MMF)
- LR4 PSM at 4x10Gbps (for 8 cores SMF)
- SR10 at 10x10Gbps (for 20 cores MMF)
- SR4 at 4x25Gbps (for 16 cores MMF)
- PSM4 at 4x25Gbps (for 8 cores SMF)
- SR8 at 8x50Gbps (for 20 cores MMF)
- SR4.2 at 2x4x50G (for 16 cores MMF)
- DR4 at 4x100Gbps (for 8 cores SMF)
However, it will be noticed that many companies name connectors with this interface as MTP fibre optic connectors, or together as MTP/MPO fibre optic connectors. What is the reason for this, and where does MTP come from.
1.MPO and MTP fibre optic connectors
MPO is the abbreviation of English Multi-fiber Push On, designed by NTT Japan's first generation of multi-fibre optical connectors. Its main industrial standards for IEC-61754-7, the current national standard for YD/T1272.5-2009, the U.S. standard for EIA/TIA-604-5.
MTP is the abbreviation of Multi-fiber Termination Push-on, it is the registered trademark of US Conec for his own MPO connector, which has done a lot of optimisation on MPO connector through several innovative designs and has its own patent protection. So, MTP connector is MPO connector, just has better mechanical and optical performance than ordinary MPO connector.MTP connector, fully comply with all MPO connector professional standards.
MTP is a high performance MPO connector.
2.MPO connector composition
MPO connector is a multi-core multi-channel plug-in connector. Its main feature is a standard diameter of 6.4mm × 2.5mm rectangular core, the use of the core end face on the left and right of the two diameter 0.7mm guide hole and guide pin (Pin) for precise positioning, the two guide pin spacing is 4.6mm.
It is mainly used for multi-core side-by-side optical fibre connection, common 8-core, 12-core, 24-core, etc., and some companies have been able to provide 72-core, or even 96-core optical fibre connection, the pitch between the fibres is 250 um. In the MPO connector docking, there is a spring mounted on the end of the ferrule to the ferrule exerts an axial pressure on the ferrule until the connector's outer frame sleeve is locked with the adapter. There is a key on the side of the ferrule which serves to determine the correct wire sequence when connecting. There is a white dot on the side of the housing to identify the position of the fibre, for example, the MPO12 fibre optic connector shown below, with the white dot on the same side as P1 (fibre position 1) and on the other side as P12.
MPO connectors include: tail guard, receiver, stop ring, spring, guide pin, retainer, MT insert, outer frame sleeve, dust cap and other components.
In addition, according to the MT insert grinding method, MPO connectors can be subdivided into:
MPO Plane Connector (MPO Plane Connector): MPO connectors where the end face of the insert is flat;
MPO Angled Connector (MPO Angled Connector): MPO connectors with angled insert faces (usually 8° angle);
3.MTP connector optimised for what places
(1) The guide pin of MTP connector is stainless steel elliptical, the design can improve the alignment accuracy and reduce the wear on the guide hole.
In traditional MPO connectors, the guide pin is chamfered, but the table surface of the pin is still sharp, and repeated insertion and removal will cause cracking or damage to the end surface near the guide hole, which in turn affects the stability of the connector insertion and loss. The figure below is a comparison of MTP and MPO connector insertion and removal reliability test, MTP connector insertion and removal of 600 times, the guide hole near the end of the surface is basically intact; while the MPO connector insertion and removal of 500 times, the guide hole near the end of the surface has obvious damage.
Comparison of MTP and MPO connector insertion and removal reliability test
(2) The spring design of the MTP fibre optic connector maximises the ribbon gap for multi-core ribbon fibre applications, thus preventing damage to the fibre.
The following figure is a comparison of the internal structure of MTP and MPO connectors, we can see that the spring cross-section design of MTP is not a conventional circular, but an oval design, which can maximize the space given to the ribbon fibre and reduce the damage to the optical fibre caused by the spring activity during the mating.
In addition, there is a groove on the retaining clip of the guide pin of the MTP connector, which can fix the spring in the groove and can centre the spring force.
4.What properties to pay attention to
a. Optical performance indicators
According to the national standard YD/T 1272.5-2009.
(1) Optical specifications of MPO single-mode connector plugs
(2) Optical specifications for MPO multimode connector plugs
b. End face geometry
The national standard YD/T 1272.5-2009 only specifies the end face geometry of the standard plug used as a test reference, and does not specify the plug to be tested.
Finally, if the MPO fibre optic connector is tested in detail, you can refer to the national standard YD/T 1272.5-2009 and GR-1435-CORE to carry out the test, which mainly includes appearance, temperature and humidity, mechanical and other tests.