Technical Note

Technical Note Document Number: TN-1008 Title: Two-Row Singlemode Ferrule Y-offset and 20N Spring Force Issue Date: 10/7/2016

Revision: 1.0

Optimal insertion loss performance for two-row, singlemode, APC, MTP® connectors assumes physical contact on all fibers. However, it has been a challenge to achieve physical contact across all 24 fibers when complying with current interface standards. Adequate spring force is one factor among others (e.g. fiber alignment, end face geometry, fiber tip quality) that helps ensure physical contact of the fiber tips. Spring force is specified in IEC 61754-7 (MPO connector family) as 9.8N nominal for one-row and two-row MPO connectors. In October 2009, US Conec® proposed increasing the spring force for two-row MPO connectors to improve insertion loss performance. Consequently, that same year, IEC 61754-7 was split into subparts that cover different variants of MPO connectors. IEC 61754-7-2 (not yet published) specifies an MPO connector with two rows of up to 12 fibers per row. At that time, no testing was performed on the two-row angled interface. Currently, in TIA-604-5-E (MPO intermateability standard), spring force is specified as 22±3N for flat, multi-row MPO interfaces and 9.8±2N for angled, multi-row MPO interfaces. The TIA standard also notes that the spring force value for angled, multi-row connectors is still being studied. These standards specifications are summarized in Table 1. In April 2015, IEC resumed discussions and testing on two-row angled MPO interfaces. Through modeling and empirical study, US Conec and IEC determined that in order to achieve improved physical contact across all fibers, the spring force should increase from 9.8N to 20N. However, the higher spring force and 8° angled interface caused the ferrules to slip in the Y-axis when mated (see Figure 1), resulting in suboptimal insertion loss performance. To account for this ferrule translation, the position of the fiber holes in the ferrule is offset in the Y direction in relation to the guide pin holes (see Figure 2). The US Conec SM MT Elite®, pre-angled ferrule with the 9.8N spring force already has this y-offset feature. Increasing the spring force resulted in new ferrules where the y-offset is optimized for a 20N spring.

Figure 1, Ferrule Translation (guide pins removed for clarity)

Figure 2, Y-offset (one fiber row shown for simplicity, not to scale) The combination of using a higher spring force and ferrules with the optimized Y-offset achieves optimal insertion loss performance of two-row, singlemode, APC connectors. In April 2016, IEC decided to move forward with 20±2N spring force for both flat and angled two-row interfaces. These changes are being http://www.usconec.com US Conec, Ltd. reserves the right to improve, enhance, or modify the features and specifications of its products without prior notification. MTP®, MT Elite®, MTP Elite®, MTP-16™, PRIZM®, LightTurn®, PRIZM® MT, MXC®, and IBC™ are trademarks or registered trademarks of US Conec Ltd.

Technical Note Document Number: TN-1008 Title: Two-Row Singlemode Ferrule Y-offset and 20N Spring Force Issue Date: 10/7/2016

Revision: 1.0

incorporated into IEC 61754-7-2 and will move forward to balloting. And US Conec will work with TIA to incorporate these changes into TIA-604-5. IEC 61754-7 TIA-604-5-E Mar. 2008 Nov. 2015 Angled, two-row interface 9.8N spring force 9.8±2N spring force Flat, two-row interface 9.8N spring force 22±3N spring force Table 1, Spring Force Specifications in Standards

IEC 61754-7-2 not yet published 20±2N spring force 20±2N spring force

US Conec designed the following spring and ferrules in accordance with the emerging IEC 61754-7-2 MPO two-row connector standard. US Conec offers ferrules for a 9.8N spring force and ferrules optimized for a 20N spring force. The 20N ferrule has a recess on the window side of the ferrule to distinguish it from a 9.8N ferrule. This recess is visible on an assembled MTP connector forming a dog-bone profile when looking at the front of the connector (see Figure 3). Note that mating a 9.8N ferrule with a 20N ferrule could show higher loss due to the unmatched Y-offset dimensions on the different ferrule designs.   

Ferrule, SM MT, 24f, pre-angled, optimized for 20N spring: Ferrule, SM MT Elite, 24f, pre-angled, optimized for 20N spring: Spring, MTP, SM, High Fiber Count, 20N:

Part Number 16843 Part Number 17182 Part Number 17881

Figure 3, 9.8N vs. 20N Ferrule Part Identifier

http://www.usconec.com US Conec, Ltd. reserves the right to improve, enhance, or modify the features and specifications of its products without prior notification. MTP®, MT Elite®, MTP Elite®, MTP-16™, PRIZM®, LightTurn®, PRIZM® MT, MXC®, and IBC™ are trademarks or registered trademarks of US Conec Ltd.