1

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

White Paper

senko.com

The Importance of Low Loss MPO
and SN-MT Connectivity in
Today’s and Future Networks
OCTOBER 2023
Rev. 01

Andrei Vankov

2

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

America
USA EAST 1-888-32-SENKO
USA WEST 1-858-623-3300
TEXAS 1-972-661-9080
Sales-Americas@senko.com
South America
BRAZIL +55-21-3736-7065
Sales-Brazil@senko.com
Asia
HONG KONG +852-2121-0516
SHANGHAI +86-21-5830-4513
SHENZHEN +86-755-2533-4893
Sales-Asia@senko.com
Europe
FRANCE +44 7939364565
Salesfrance@senko.com
GERMANY +49(0)15117683072
Sales-Germany@senko.com
ITALY +39 338 8919089
Sales-Italy@senko.com
POLAND +44 (0) 7796444488
Sales-Europe@senko.com
SPAIN & PORTUGAL +34 678042829
Sales-Iberia@senko.com
UK +44 (0) 1256 700880
Sales-UK@senko.com
OTHER +44(0) 1256 700880
Sales-Europe@senko.com
Asia Pacific
AUSTRALIA +61 (0) 3 9755-7922
Sales-Asia-Pacific@senko.com
Middle East North Africa
DUBAI +971 4 8865160
Sales-MENA@senko.com
Japan
TOKYO +81 (0) 3 5825-0911
Sales-Japan@senko.com

3

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

The Importance of Low
Loss MPO and SN-MT
Connectivity in Today’sand Future Networks

Contents

4

Parallel Optics Development

4- Definition of Parallel Optics

5- Advancements in Optical Transceiver Technology

10- Onboard Optics, Backplane MT Based Connection
and BTW

11

Link Budgets with MPO

11- Low Loss Ferrule Requirements

11- Random Mating Loss and SN-MT Interconnect

23

Advancement in Cable Technology

24

Recognized Industry Standards

25

Summary26

References

4

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

1.1 Parallel Optics Development
Definition of Parallel Optics
In the late 1980s, Nippon Telegraph and Telephone Corp. (NTT)invented a physical contact connection technology that significantly
improved the performance and reliability of fiber optic connectors.
These connectors were named Single Fiber Coupling (SC) andMultifiber Push-On (MPO). The compact size and easy push-pull
installation were major advantages of both connectors. The SC
connector accommodates a single fiber, while the MPO connector
can terminate up to 72 fibers simultaneously. Since the early 1990s,
MPO connectors have been widely adopted by carriers and data
centers. This technology revolutionized global digital communication
systems by simplifying interconnect routing. The ability to bundle

multiple fibers onto a single connector is the greatest advantage of
MPO connectors. In high-density scenarios, MPO connectors save
space compared to duplex connectors or other alternatives.
Thus, parallel optics was born as the demand for data increased,leading to a migration from duplex transceivers and interconnects tomulti-fiber transceivers with MPO interfaces. Parallel optics with MT
ferrule-based connectors refers to a technology that utilizes multiple
optical fibers in parallel to transmit data simultaneously. The MPO
connector became the connector of choice for parallel optic systems.

Key Features of Parallel Optics Include:

Parallel
Transmission

Unlike traditional serial transmission, where a single high-speed signal is transmitted over a single fiber,
parallel optics utilize multiple fibers (or multiple lanes within a fiber) to transmit data in parallel. This
allows for increased data throughoput.

High Data Rates

Parallel optics is used to achieve very high data rates, such as 100 Gbps, 400 Gbps, or even higher. By
splitting the data into multiple channels, each operating at a lower data rate, the overall system canachieve higher aggregate bandwidth.

Multi-Channel
Transceivers

Parallel optics requires specialized multi-channel transceivers that include multiple laser diodes fortransmitting and multiple photodetectors for receiving. These transceivers are often referred to as“parallel optics modules.”MPO Connectors

To facilitate the connection of multiple fibers between transceivers, parallel optics often use MPO or
multi-fiber termination push-on (MTP) connectors. These connectors allow for efficient coupling ofmultiple fibers, enabling parallel transmission.

Data Center
Applications

Parallel optics is particularly well-suited for data center applications, where high-speed and high-capacity
connections between servers, switches, and other networking equipment are crucial.

It’s worth noting that parallel optics technology is just one approachto achieving high data rates over optical fibers. Another approach isusing wavelength division multiplexing (WDM), where multiple data
streams are transmitted using different wavelengths of light over a

single fiber. The choice between parallel optics and WDM depends
on factors such as system architecture, distance requirements, costconsiderations, and compatibility with existing infrastructure.

5

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

1.2 Advancements in Optical Transceiver Technology and Optical Connectors
An optical transceiver is a vital hardware component responsible
for transmitting and receiving data. Since their initial development,
optical transceivers have come in various forms, evolving overtime. To ensure seamless integration with network equipment andtransceivers from different vendors, industry standards have been
established to govern all functionalities and characteristics of opticaltransceivers. Numerous organizations have been actively working
on achieving transceiver interoperability. Leading the charge are

GBIC

the Institute of Electrical and Electronics Engineers (IEEE) and MultiSource Agreements (MSAs), who define a significant portion of thestandards for optical transceivers. Over the past 25 years, the market
has witnessed the introduction of diverse optical transceiver types,
as depicted in Figure 1. These innovations have revolutionized datatransmission and reception, making optical transceivers indispensable
components in modern networks.

SFP

SFP (Small Form-factor Pluggable) transceivers
emerged in 2000, offering the same functionality
in a smaller form. LC Duplex and MT-RJ connectors
were commonly used.

In 1995, the Small Form Factor Committee
introduced GBIC (Gigabit Interface Converter),the first flexible hot-swappable transceiverstandard, later revised in 2000.

1995

2000
QSFP28QSFP562014

QSFP56 was standardized in 2019, doubling
the data rate of QSFP28 to 200Gbps, using
parallel fibers or PAM4 modulation.

2019

SFP+

SFP+ (Enhanced Small Formfactor Pluggable) was launchedin 2006, delivering higher
data rates up to 10 Gbps andsupporting various connectors.

In 2012, Enhanced QSFP+ and
CFP2 were introduced, offering
higher performance and densitywith data rates ranging from
100Gbps to 200Gbps.

2012

XFP (X Form-factor Pluggable) was
developed in 2002 and adopted in
2003, providing 10G modules denotedby the Roman numeral “X”.

2002

QSFP+ and CFP2

QSFP28, based on the same
technology as QSFP+, became thestandard for 100G applicationsin 2014, offering configurations
from 100m to 80km.

XFP

2006
QSFP-DD and OSFP

Also in 2019, QSFP-DD and OSFP were released,enabling higher data rates of up to 800Gbps with
new CS connectors.

2019

6

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Summary of The Evolution of Optical Transceivers

Figure 1 Optical transceivers development time line.
The latest standard, SFP-DD, allows data centers to double port density
and increase data rates by utilizing OM3 and OM4 optical fibers.

With the evolution from duplex to parallel optics, transceivers now offer
higher data rates and increased connectivity density, reducing costs
and enabling fast network upgrades.

Figure 2 Transceiver types for parallel optics. Reference: Jeff Maki, Juniper. (2020).

7

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

What Are the Driving Factors For 400G Development?
The driving factors for 400G development are video streaming services
and video conferencing services. These services require high data transfer
speeds to function smoothly across the globe. A look at the stats reveals
that a medium-quality stream on Netflix consumes 0.8GB per hour. Seethat in relation to over 21 million subscribers. As the traveling costs came
down, the savings went to improved quality streams on Netflix like HD
and 4K. What stood at 0.8GB per hour rose to 3 and 7GB per hour. Thisevolved the need for 400G development. Another example is a trend after
COVID of working from home. The Bureau of Labor Statistics found thataround 27% of the U.S. workforce was working remotely at least part time
as of August and September 2022, while a handful of academic surveys
have suggested that the number is closer to 50%. As video conferencing
took center stage, Zoom, which consumes 0.5GB per hour, saw a hugeincrease in its user base.

The data transfer that keeps up with bandwidth demand occurs inHyperscale Data Centers. Hyperscale data centers are large-scale
facilities specifically designed to handle massive amounts of data andcomputational workloads. These data centers are capable of providing
high levels of performance, scalability, and reliability to meet theneeds of modern internet-based services and applications. The mostadvanced data centers are moving toward 400G with an eye to 1.6TBof data processing rates. To put it simply, 400G raises the data transfer
speed four times over typical 100G. 400G reduces the cost of 100G
ports as breakouts when comparing a 4 x 100G solution to facilitate
400GbE with a single 400G solution to do the same. A single node at
the output minimizes the risk of failures as well as lower the energy
requirement. This brings down operational cost while maintains same
redundancy capabilities and more flexible scalability.

Figure 3 From Data Center to Hyperscale migration.
Naturally the optical connector footprint to accommodate all theabove requirements should be smaller with and have as many fibers
as possible. Duplex SC connectors were replaced by duplex LC
connectors in the late nineties. LC connectors feature a 1.25mm ferrule,
which is half the size of the 2.5mm ferrules used in SC connectors. LC
connectors became known as Small Form Factor (SFP) interconnects.
Today, as the migration to Hyperscale Data Centers continues, a newgeneration of interconnects has been developed, called Very Small
Form Factor (VSFF) connectors. These connectors are known as CS and

SN connectors. Both connectors feature 1.25mm ferrules, but the pitch
between the ferrules is reduced to accommodate more space in thesame rack unit area compared to LC or MPO interconnections. Similarly,
the MPO footprint is also being reduced in size, opening the way for
new SN-MT interconnections. A 1RU patch panel can house a maximumof 80 MPO adapters, which represents 2,560 fibers when using 32-fiber
MPO connectors. In comparison, a 1RU patch panel can also house 216
SN-MT adapters, which represents 3,456 fibers when using 16F SN-MT
connectors. This is a 25% increase in fiber count in just 1RU.

8

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

What Are the Driving Factors For 400G Development?
In Hyperscale network architecture, the leaf-spine cross-connection
represents a specific design approach utilized to establish an
exceedingly scalable and efficient network fabric. The leaf-spine
topology embodies a distinct network design aimed at preventing
the constraints inherent in conventional hierarchical networkarchitectures. Within this framework, devices (such as servers, switches,and routers) are segregated into two primary tiers: leaf switches andspine switches. Leaf switches serve as the direct connectors to end
devices, including servers and other network peripherals. Typically,each leaf switch maintains connections to every spine switch. Spineswitches, in contrast, serve as conduits for high-speed, non-blocking
interconnectivity among leaf switches. These spine switches facilitate
seamless communication between any given leaf switch and any otherleaf switch, all while minimizing the number of intermediary hops.
In this particular network design approach, the connection between
leaf switches and spine switches is orchestrated to furnish elevatedbandwidth and curtail network latency. For scenarios involving a highchannel count, the SN-MT connector emerges as the most optimal
choice for optical interconnect.

Today, SN-MT is considered theconnector with the highest density
in the industry.
The benefits of SN-MT are:•
Up to 16-fibers in a single row•
Same connector footprint as SN connector•
2.7x denser than MPO-16F•
1.3x denser than MPO-32F•
Low insertion loss across all channels– maximum 0.35dB max (IEC Grade B)

SN-MTStandard 2mm
SN-MT Bare Ribbon
SN-MT Junior
SN-MT BTW

Figure 4 SN-MT designs.
What other factors should be considered? The innovation in fiberand specifically fiber ribbon design. The standard 250μm pitch usedin multi-fiber ferrules with 125μm cladding diameter optical fiber isphysically too large to support the quantity of optical lanes that will be
coupled inside the coming switching platforms. That’s why SN-MT has
a next generation MT-style ferrule designed for smaller acrylate coatingfiber ribbons on a pitch of 200μm. By decreasing the pitch from 250μm
to 200μm, up to 50% rack unit (RU) space can be saved. See figure 5.
Figure 5 Footprint comparison to scale between MPO and SN-MT fiber count.

9

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

What Are the Driving Factors For 400G Development?
This tighter pitch enables higher fiber densities coupled directly to orin Tx/Rx lines. The new MT ferrule also needs to be “new and improved”

over standard MT ferrules in terms of optical loss and reliability and
we discuss it further in Chapter 2.

6a6b 16F in one row

6c

2.7x

Density increase
compared to MPO-16F

Figure 6 VSFF Connectors with MT Ferrules are enabling unprecedented fiber density: a) graph depicting different fiber counts on a 1 RU panel fordifferent optical connector types, b) SN-MT connector with 16F per row, c) MPO and SN-MT connector comparison.

10

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

1.2 Onboard Optics, Backplane MT Based Connection and BTW
Another trend that necessitates smaller and more reliable MT ferrules
is On-Board Optics (OBO). The fibers are being brought closer tothe optical chip. Achieving the transmission of data by light to thepoint where it is processed stands as one of the ultimate goals of
optical networks. Progress in implementing optics into electronics isindicating a trend of minimizing the distance between the optical andelectrical components on the active PCB. There is a drive to bring theoptical connector to the same level as the location of the Tx/Rx chipand create a unified component.
Currently, the standard solution is based on pluggable modules in theform of backplane connections or BTW (Behind the Wall). However,this solution has several disadvantages, including larger dimensions
and high energy consumption and cooling requirements. The second
generation of solutions involves OBO modules, where the optoelectrical converter is already integrated at the PCB level but remains
a separate part. The fully implemented optical part, known as the copackaged solution, will be covered by the 3rd generation, which isstill under final development. In all cases, the power requirements forcooling are significantly reduced.

The primary option for coupling fiber to the chip involves using
standard MT ferrules, but the superior option is a smaller and denser
SN-MT ferrule. The MT approach relies on the physical contact
principle, whereas the fiber alignment from a chip can utilize a focal
lens principle.
Moving the fiber to the chip significantly reduces energy consumption
for cooling (see Figure 8). By directly integrating the function oftransceivers onto a substrate with the IC switch, there is no need forelectrical signal travel over the PCB. Consequently, this eliminates
heat generation resulting from optical-to-electrical conversion, whichis performed immediately without the need for wiring transceiver.

Pluggable Module

Onboard Module
Presently, companies like Cudoform, Ranovus, and many others areactively working on developing solutions in this field.

Co-Packaged Optics

SENKO SN-MT Option for
midplane connection

Figure 8 Pluggable vs onboard vs
Co-Packaged Optics.
Cudoform fiber to chip array
Figure 7 Midplane and onboard optics with SENKO MT ferrule.

LOWER
POWER

11

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

2.0 Link Budgets With MPO
2.1 Low Loss Requirements
The optical link budget for MPO transceivers can vary depending on
the specific application, data rate, and distance of the link. The linkbudget is a calculation that takes into account various parameterssuch as transmitter power, receiver sensitivity, fiber attenuationand connector losses to ensure that the received optical power issufficient for error-free data transmission. For example, in a typical
40 Gigabit Ethernet application over OM3 or OM4 multimode fiber,
the link budget for MPO transceivers might be around 3 to 4 dB. Thismeans that the overall optical loss in the system should not exceed 2 to
3dB in order for received optical power at the receiver be at guaranteed
sensitivity level to account for losses in the fiber link. For longer-distanceapplications, such as 100 Gigabit Ethernet over OM4 multimode fiber orsingle-mode fiber links, the link budget for MPO transceivers could beslightly higher depending on the specific requirements.

It’s important to note that the link budget also considers factors suchas system margin, temperature variations, and other potential losses
in the link. However, the biggest contributing factor is connector loss.
Guaranteed low connector loss ensures reliable and error-free datatransmission in optical communication systems. The actual link budget
should be determined based on the specific connector loss and theenvironmental conditions to which the connectors are exposed.

2.2 Random Mating Loss and SN-MT Interconnect
As mentioned earlier, MT-based connectors are the future forHyperscale Data Centers. The optical loss of any fiber optic connector
is highly dependent on the lateral misalignment. The higher the
misalignment, the more mismatch will be observed between thefiber cores. The relationship between the fiber core misalignment andoptical loss is calculated.

Loss, dB = -10 log 1-

8x
3 πr

r = fiber radius x = offset amountFigure 9 MM and SM laterlal offset graphs.

Figure 10 Theoretical calculation formula for laterla offset cores
misalignment.

12

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
The tolerance of the MT ferrule’s guide pin and fiber holes holds greatsignificance. SENKO offers two types of ferrules in their MPO kits:
Standard and Super Low Loss. The primary differences between these
two lie in the tolerances for individual fiber holes [1] and guide pinholes [2]. See figure 11. Notably, the Low Loss grade adheres to muchstricter tolerances.

In the past, manufacturing techniques for MT Ferrules and thesizes of fiber ODs were limited by available materials and molding
technology. Consequently, the tolerances were not as tight as they
are today, which presented challenges in achieving low optical losses.
However, advancements in technology have significantly improved
the tolerances between the fiber ODs and the MT ferrule IDs.

In MPO connectors with MT ferrules, the misalignment of fiber coresalong the axis stands as the main contributor to connection loss.
Theoretical calculations suggest that to achieve a target connection
loss of, for example, ≤ 0.5 dB, the total misalignment of fiber cores mustbe ≤ 1.6μm, with an allowable stackable tolerance for fiber positions
and guide pins of ≤ 0.8μm per ferrule. Based on the tolerance analysis
results, the practically permissible axis misalignment that meets thetarget loss of ≤ 0.5dB has been set at ≤ 0.9μm per ferrule.

These tighter tolerances now allow for successful termination, withinsertion losses expected to be below 0.35dB per channel in randommating scenario, regardless of the number of channels. To achievethis, it is crucial to ensure that the ferrule axis misalignment between
the fibers is ≤ 1.40μm, in addition to employing proper terminationand polishing techniques. Specifically, for individual Low Loss MT
ferrules, the overall fiber misalignment should be ≤ 0.70μm.

1Figure 11 MT ferrule possibilities oflateral misalignments between fibers.

2

13

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
SENKO believes that the criteria for Insertion Loss (IL) should be basedon random mating, as described in the document IEC 61753-1 titled“Attenuation of Random Mated Connectors.” This document defines aminimum number of channels below the allowable maximum IL value inpercentage (97%) for randomly mated connectors in a field setting andcategorizes them into four different grades: A, B, C and D. It is important
to note that the IEC 61753-1 categorizes connection performance grades
for single-mode and multimode jumpers in a controlled environment
and for ceramic ferrules only at the time of publishing this work.

The standard provides four grades for IL, ranging from A (best) to D
(worst), as well as grades for Return Loss (RL), ranging from 1 (best)
to 4 (worst). Although Grade “A” is not officially ratified by the IEC
document, it is likely to have similar optical performance, as reflected
in Table 1 below.

Table 1 IEC 61753-1 proposed ceramic ferrule grades.

Attenuation Grade

Attenuation Random Mated IEC 61300-3-34

Grade A*0.07 dB mean

0.15 dB maximum for >97% of samples

Grade B

0.12 dB mean

0.25 dB maximum for >97% of samples

Grade C

0.25 dB mean

0.50 dB maximum for >97% of samples

Grade D

0.50 dB mean

1.00 dB maximum for >97% of samples

Return Loss Grade

Return Loss Random Mated IEC 61300-3-6

Grade 1

≥ 60 dB (ated) and ≥ 55 dB (unmated)

Grade 2≥ 45 dB

Grade 3≥ 35 dB

Grade 4

≥ 26 dB

Specification

Each-to Each Values

Budget for 10 Connections

approx. 0.2 dB (possibly higher if different
manufacturers are combined or unadjusted
connectors are used)approx. 2 dB, unclear range of tolerance

Grade C

Mean 0.25 dB, Max 0.50 dB

0.25 dB

Grade B

Mean 0.12 dB, Max 0.25 dB

1.2 dB

Grade A*

Mean 0.07 dB, Max 0.12 dB

0.70 dB

0.1 dB Connector*

Note: Grade A is not specified at time of writing, but is assumed to be as shown14

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
It is important to note that the IEC 61753-1 document was developed
specifically for ceramic ferrules and not for MPO connectors. However,
we believe that its principles can be applicable to MPO testing. MPO
connectors typically have a minimum fiber count of 12. When a connector
manufacturer states that the MPO connector’s maximum loss is, forexample, 0.5dB, it is more practical to consider the mean result among
the same interconnect with an allowable double value from 0.5dB, which
would be 1.00dB in a few channels. This approach allows for greater
production efficiency, as it accounts for the possibility of a few channels
slightly exceeding 0.5dB while remaining below 0.5x2=1.00dB in over
97% of the readings. By using this method, it offers a more practical
approach while considering the production efficiency and the fact that inreal-world scenarios, with today’s transceivers’ dynamic ranges, it is more
likely that such a tested MPO connector will perform reliably.

Below is another example of the random mating study. Let’s assume
that MPO Grade B specifies a maximum loss per channel of 0.35dB,
while Grade C specifies a maximum loss of 0.50dB. In Grade B, a few
channels exceeded the maximum stated loss of 0.35dB, but over 97%
of the channels measured were under 0.35dB, with the mean value
below 0.35dB.

Table 2 Example of compilation of Random Mating data.

IL (dB)
Pass Rate

Grade

Mean

Result1310 nm

1550 nm1310 nm

1550 nm

Grade B
Mean 0.35 DB
Minimum 95%< 0.35 dB

98.06%

97.08%

0.15

0.11

PASS

Grade C
Mean 0.50 DB
Minimum 95%< 0.50 dB

100.00%100.00%

0.15

0.11

PASS

15

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
At SENKO, we are conducting a study to evaluate the optical loss
performance of connectors in a randomly mated scenario, simulating
real-world field performance per the IEC 61753-1 document. The
most common and statistically meaningful approach for this study is
typically carried out in a 10x10 configuration.

to random mating. Additionally, it aims to understand the impact
of different connector types on insertion loss in such scenarios. As
mentioned earlier, MT-based connectors come in various varieties andfiber counts. They can be categorized as SM Low Loss, SM Standard,
MM Low Loss, and MM Standard. The studies were conducted with all
categories of SENKO MT ferrules.

In a 10x10 configuration, multiple sets of 10 MPO connectors are
randomly mated with each other one at a time, resulting in over 100
different combinations. The purpose of this study is to assess theperformance and reliability of optical connections when subjected

Below are the results from the study performed at SENKO for the 12F
MPO connector:

100

Frequency

80

60

40

20

0
0.00 0.05 0.10

0.15 0.20 0.25 0.30

0.35 0.40 0.45

0.50 0.55 0.60 0.65 0.70 0.75 0.80

MPO Random Mating Insertion Loss (dB)Specification

SM Low Loss

SM Standard

MM Low Loss

MM Standard

IL Typical vs Reference Connector

0.10 dB

0.20 dB

0.08 dB

0.15 dB

IL Max vs Reference Connector

0.25 dB

0.70 dB

0.25 dB

0.5 dB

Random Mating Grade IEC 61755-3-31

Grade B

Grade Cn/an/a

Return Loss

60 dB

60 dB

25 dB

25 dB

SM Low Loss Pin

SM PinSM PinMM PinRecommended PIn Used
Figure 12 Performance of 12F MPO Connector.

16

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
Below are the results from the study performed at SENKO for the 16/32F MPO Connector:

120

100

Frequency

80

60

40

20

0
0.00 0.05 0.10

0.15 0.20 0.25 0.30

0.35 0.40 0.45

0.50 0.55 0.60 0.65 0.70 0.75 0.80

MPO Random Mating Insertion Loss (dB)Specification

SM Low Loss

SM Standard

MM Low Loss

MM Standard

IL Typical vs Reference Connector

0.15 dB

0.15 dB

0.20 dB

0.25 dB

IL Max vs Reference Connector

0.35 dB

0.35 dB

0.60 dB

0.60 dB

Random Mating Grade IEC 61755-3-31

Grade B*

n/a

n/a

n/a

Return Loss

60 dB

25 dB

25 dB

25 dB

SM Low Loss Pin

SM PinMM PinMM PinRecommended PIn Used
Figure 13 Performance of 16F MPO Connector.

17

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
Below are the results from the study performed at SENKO for the 24F MPO Connector:

160
140

Distribution

120
100
80
60
40
20
0
0.00 0.05 0.10

0.15 0.20 0.25 0.30

0.35 0.40 0.45

0.50 0.55 0.60 0.65 0.70 0.75 0.80

MPO Random Mating Insertion Loss (dB)Specification

SM Low Loss

SM Standard

MM Low Loss

MM Standard

IL Typical vs Reference Connector

0.15 dB

0.25 dB

0.15 dB

0.20 dB

IL Max vs Reference Connector

0.35 dB

1.00 dB

0.35 dB

0.50 dB

Return Loss

60 dB

60 dB

25 dB

25 dB

SM Low Loss Pin

SM Pin dB

SM PinMM PinRecommended PIn Used
Figure 14 Performance of 24F MPO Connector.

18

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
Below are the results from the study performed at SENKO for the 12F MPO Low Loss Connector:

SM

300

Maximum
connector
Insertion Lossfor 100GE

250

Distribution

200
MM

150

100
12F MPO SM Low Loss by 1310nm
12F MPO MM Low Loss by 850nm

50

0
0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

MPO Random Mating Insertion Loss (dB)

SPECIFICATION

SM LOW LOSSSM STANDARD

MM LOW LOSSMM STANDARD

IL Typical vs Reference connector

0.10dB

0.20dB

0.08dB

0.15dBIL Max vs Reference connector

0.25dB

0.70dB

0.25dB

0.50dBIL Typical Random Mating

0.12dB

0.20dB

0.10dB

0.15dB

Random Mating IEC Spec: IEC61755-3-31

Grade B (0.25)

Grade C (0.5)

n/a

n/a

Return Loss

60dB

60dB

25dB

25dB

Recommended PIN Used

SM Low loss Pin

SM PinSM PinMM Pin* Above number is only achievable when using SENKO Recommended Reference Jumper, Polishing process and testing method* SM Low loss and MM Low loss Max IL 0.25dB to be 95% of all fiber

Figure 15 SENKO study for the 12F MPO Low Loss Connector.

Based on the data, SENKO achieves an insertion loss distribution ofa maximum of only 0.25dB across all 12 channels for super low loss
connectors which is remarkable.

Below are the results from the study that shows random mating losses
mating SENKO MPO with leading MPO brands:

19

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
Based on the data, SENKO achieves an insertion loss distribution ofa maximum of only 0.25dB across all 12 channels for super low loss
connectors which is remarkable.

Below are the results from the study that shows random mating losses
mating SENKO MPO with leading MPO brands:

SENKO vsSENKO
AVG: 0.04 dB
Max 0.25 dB
STD: 0.03 dB

350

12MT - SM Low Loss
1550nm, 2160 Fibers

SENKO vs SENKO
SENKO vs Leading Brand
Leading Brand vs Leading Brand

300
SENKO vs
Leading Brand
AVG: 0.08 dB
Max 0.33dB
STD: 0.06 dB

Distribution

250
200
150

Leading Brand
vs Leading Brand
AVG: 0.10 dB
Max 0.35 dB
STD: 0.073 dB

100
50
0
0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

Insertion Loss (dB)Figure 16 SENKO MPO optical loss performance against leading MPO brands.

The data suggests that SENKO MT ferrule tolerances are superior tothose of competitive MPO connectors. When comparing SENKO MPO
connectors mated with SENKO MPO connectors to the scenario where
they are mated with leading brands, the average insertion loss (IL),maximum IL, and standard deviation are slightly higher in the lattercase. It is essential to remember that lateral misalignment is the main
contributing factor for insertion loss, and it is apparent that the ferrule
hole, pins, and guide hole tolerances are superior in SENKO MT ferrules.
The newest generation of MT ferrules, known as SN-MTs, has recently

been developed for smaller footprint MPOs. These SN-MTs hold thepotential to become the prime choice for Hyperscale Data Centers. The
new ferrule is smaller than the traditional MT with a reduced guide pinbore diameter and guide pin bore pitch. Figure 17 illustrates the MT
and MT- 16 dimensional differences.

20

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
The newest generation of MT ferrules, known as SN-MTs, has recently
been developed for smaller footprint MPOs. These SN-MTs hold thepotential to become the prime choice for Hyperscale Data Centers. The
new ferrule is smaller than the traditional MT with a reduced guide pinbore diameter and guide pin bore pitch. Figure 17 illustrates the MT
and MT- 16 dimensional differences.

MPO-12/12 Two Row

MPO-16/16 Two Row(TIA-604-5)(TIA-604-18)

Key
CenteredKey
OffsetFootprint size comparison with MPO
TMT Ferrule

5.3 mm

5.3 mmMPO

SN®-MT

8.2 mm

MT-16 Ferrule0.25 mm0.55 mm0.25 mm

9.46 mm0.55 mm
12.4mm

3.85 mm

1 x SN-MT (16-fibers)
Figure 17 Comparison between MPO and SN-MT dimensions.
The SN-MT ferrule is designed with less material, smaller guide pinholes, and a tighter pitch between the fibers. It is specifically intended
for use with smaller ribbons of 200μm, rather than the traditional
250μm protective acrylate buffer coating. The traditional MT ferruleis standardized in multiple standards, including IEC 61754-5, which
defines the overall size and footprint of the typical rectangular
ferrule used in ferrule-to-ferrule applications. The mechanical matinginterface requirements of the traditional MPO connector format are
defined in the IEC 61754-7-1 and 61754-7-2 series. Additionally, the
IEC Optical Interface specification series 61755-3-31 specifies theprecision terminated ferrule dimensions required to achieve various
optical performance grades. For the one fiber row MT-16 ferrule matinginterface, the standard is covered in the IEC 61754-7-4 document.

21

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
As the IEC standards are catching up with dimensional ferrule
requirements, SENKO has taken a leading role in developing andtesting the new SN-MT ferrule, which is incorporated into the SENKO
SN-MT connector. Similar 10x10 studies were performed for MM andSM assemblies, all featuring the SN-MT ferrule, and the results are very

positive. Below is the data from the studies.potential to become theprime choice for Hyperscale Data Centers. The new ferrule is smaller
than the traditional MT with a reduced guide pin bore diameterand guide pin bore pitch. Figure 17 illustrates the MT and MT- 16
dimensional differences.

Figure 18 IL Distribution at 1310nm.

Figure 19 Average IL per channel at 1310nms.

Figure 20 RL Distribution at 1310nm

Figure 21 IL Distribution at 1550nm

Figure 22 Average IL per channel at 1550nm.

Figure 23 RL Distribution at 1550nm

22

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Random Mating Loss and SN-MT Interconnect
In addition, SENKO compared the cumulative Gaussian IL distribution
across all channels between the 10x10 study on 16-fiber MPO standard
connectors and the study on 16-fiber SN-MT connectors. It should
be noted that the MPO ferrule dimensions, pins, pin hole, and spring

compression force differ from those of the SN ferrule. However, we
believed it would be meaningful to compare the two similar data sets
since they both originated from identical 10x10 studies. The results arepresented in a Table 3 below:

Total CountMeanSt Dev

Minimum

Maximum

SN-MT16 SM

1440

0.084

0.068

0.00

0.35

MPO-16 SM

1440

0.087

0.074

0.00

0.34

Connector Type

Table 3 IL comparison summary between MPO-16 and SN-MT-16 SM.

Figure 24 IL comparison between MPO-16 and SN-MT-16 SM

The optical losses between MPO-16 and SN-MT-16 SM are very similar
regardless of the ferrule differences.

23

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

3.0 Advancement in Cable Construction Technologies
As mentioned earlier, ribbon constructions are also becoming
smaller and smaller. Fiber manufacturers are exploring new designs
and conducting tests on newer fiber and cable configurations toachieve reduced 250-micron fiber coating down to 200 microns while
maintaining the standard 125-micron cladding diameter for opticalfibers. Currently, the development is nearing completion for an evensmaller design, featuring an 80-micron glass cladding layer diameter,
and utilizing fiber coated with as low as 165-micron outer diameter.
Figure 25 compares the dimensional implications of 24 fibers arranged
in a linear array with an 80-micron cladding and 165-micron protective
layer to that of 16 traditional fibers with 125-micron cladding and
250-micron protective layer. Furthermore, using smaller diameter
optical fibers bundled in cables results in reduced cable diameters,
which, in turn, reduces space consumption in cable routing areas
where space is at a premium.

Likewise, the cables themselves are now becoming more compact.
Smaller cable diameters allow for more fibers to be placed inside,
thanks to new types of ribbon technology called rollable ribbon.
Rollable fiber optic ribbon technology, also known as SpiderWeb
Ribbon® (AFL Trademark), is an emerging development in the fiber
optics industry. Rollable ribbon technology aims to address thechallenge of reducing cable size while maintaining high fiber counts.
In traditional ribbon cables, multiple fibers are stacked on top of eachother with a protective matrix, which can make the cable bulkier andless flexible. Rollable ribbon technology, on the other hand, arranges
the individual fibers in a rollable and flexible ribbon-like structure,
allowing for easier cable management, a faster termination process,and smaller cable outer diameters. By employing rollable ribbon
technology, cable manufacturers can double the fiber count in a
cable without increasing its size. This technology has the potential toprovide higher fiber density and more efficient use of available spacein cable routing areas, especially in high-density data centers or tightinstallation spaces. Logically, with this type of new ribbon, smaller
array connectors will be required, such as SN-MT.

Figure 26 Rollable ribbon section example.

Figure 25 Compares the dimensional differences of 24 fibers arranged
in a linear array with an 80-micron cladding and 165-micron protective
layer to 16 traditional fibers with 125-micron cladding and 250-micronprotective layer.

24

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

GR-1435COMPLIANT

4.0 Recognized Industry Standards
There are three standards that define the MPO connector. To ensure
MPO compatibility among suppliers, there is TIA-604-5, also known as
FOCIS-5: Fiber Optic Connector Intermateability Standard - Type MPO.
This standard is developed by a North American TIA committee.
MPO connectors are internationally defined by the IEC 61754-7
international standard, which outlines the mechanical and opticalspecifications for MPO connectors used in optical fiber communication
systems. This standard covers the basic requirements for MPO
connectors, including their physical characteristics, dimensions, andoptical performance.
Finally, there is a testing standard defined by Telcordia GR-1435. This
standard provides generic requirements and characteristics required ofsingle-mode multi-fiber optical connectors. It includes performance tests
to compare products against connector requirements and performance
objectives. These tests supplement standard service life performance
tests and are intended to identify potential weaknesses in connector
assembly, design, or materials. Typically, these tests are conducted on aset of 15 samples from the manufacturer to establish a statistically valid
sample size. The GR-1435-CORE standard defines the requirements,
features, performance criteria, and characteristics of single-mode multifiber optical connectors. The standard outlines qualification testing in twophases: initial product qualification/certification and periodic verification
to ensure that the product performs within established parameters. The
GR-1435 standard is an established industry specification for MPO-type
fiber optic connectors. For connector designers and manufacturers,
passing GR-1435 testing is important for several reasons:

Quality Assurance

Meeting GR-1435 testing standards is a hallmark of high-quality manufacturing. By passing these tests,
manufacturers demonstrate that their connectors are designed and manufactured to stringent quality
benchmarks, reducing the likelihood of defects and failures.

Interoperability

GR-1435 compliance ensures that connectors from different manufacturers are compatible andcan reliably interconnect with each other. This interoperability is crucial in building complex optical
networks using components from various sources.

Reliability

Connectors that pass GR-1435 testing are more likely to have reliable and consistent performance overtime, minimizing the risk of signal loss, data corruption, or network downtime.

Customer
Confidence

Compliance with a recognized industry standard like GR-1435 builds trust and confidence amongcustomers, who can rely on the connectors’ performance and compatibility.

MarketAcceptance

Many industries and markets require adherence to established standards like GR-1435. Complianceenhances a manufacturer's credibility and makes their connectors more widely accepted in themarketplace.

Reduced Risk

Rigorous testing helps identify and address potential design flaws or manufacturing defects early in the
production process, reducing the risk of field failures and costly recalls.

Long-Term
Viability

Connectors that meet GR-1435 standards are likely to remain viable and compatible as network
technologies evolve and higher data rates are adopted.

Global Reach

GR-1435 compliance ensures that connectors can be used in international projects and installations, as thestandard is recognized and accepted globally.

In summary, passing GR-1435 testing is crucial for connector
manufacturers to ensure the quality, performance, and compatibility of
their products within the broader optical communication ecosystem. It

helps manufacturers meet industry requirements, build customer trust,and contribute to the overall reliability of optical networks.

25

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

Summary
At SENKO, we are continuously dedicated to pushing the boundaries of
our MT ferrule technology to achieve lower losses. When determining
your network budget requirements, understanding the necessary
optical losses is of paramount importance. By utilizing SENKO MT and
SN-MT low-loss ferrules in comparison to standard alternatives andthose of the competition, you can effectively reduce average loss inrandom mating by half.
SENKO offers an extensive range of MPO interconnects designed toadhere to the GR-1435 requirements for multi-fiber optical connectors.
Our MPO kits incorporate a multitude of technological features that
position them as industry leaders in both design and performance.
These connectors feature SM and MM super low-loss as well as standard
MT ferrules, meticulously manufactured in Japan by our partners whoare pioneers in MT ferrule technology.
SENKO provides an all-encompassing lineup of MPO and SN-MT

connectors and solutions catering to various applications andoperational environments, spanning from Hyperscale Data Centers tochallenging outdoor conditions. Our MPO connector design integrates
patented features that facilitate easier termination and installation,heightened precision, proven reliability, and substantial performanceenhancements compared to competing solutions.
The multi-fiber SN-MT connectors are at the forefront of paving theway for future high-bandwidth transceivers. By significantly increasing
connector fiber density and concurrently supporting the highly
adaptable leaf and spine network distribution design, these connectors
are instrumental in enabling robust performance. Our well-establishedconnector ferrule technology empowers SENKO to manufacture
connectors boasting exceptional optical performance. The userfriendly operation and ease of maintaining end face cleanliness makethe transition to SN-MT connectors effortless for network operators.
The SENKO SN-MT connector offers several benefits, including:High Density

The SN-MT connector boasts industry-leading high density, accommodating a significant number offibers in a compact footprint.

Performance

The SN-MT connector provides a resilient and consistent performance, exhibiting random mating lossesof less than 0.35dB per channel. It facilitates high-speed data transmission while preserving signal
integrity effectively.

Space Efficiency

Its compact design and small form factor help optimize limited rack space, making it ideal for installations
where space is at a premium.

Ease of
Installation

The connector’s user-friendly design and features contribute to simplified and efficient installation
processes.

Reliability

SENKO is known for its commitment to quality and reliability, ensuring that the SN-MT connector
maintains a high level of performance over time.

Flexibility

The connector is suitable for various applications, providing flexibility in network designs and setups.

Future-Proofing

Its advanced technology and capabilities contribute to future-proofing

Scalability

Its design allows for scalability, enabling network expansions and upgrades as needed.

Overall, the SENKO SN-MT connector offers a range of advantages that make it a valuable choice for modern fiber optic networking solutions.

26

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS

References
1. IEC 61754-5:2005 Standard Fibre optics - Fibre optic connector interfaces - Part 5: Type MT connector family
2. TIA-604-5 FOCIS 5 Fiber Optic Connector Intermateability Standard Type MPO
3. IEC 61754-7-3:2019 Fibre optic interconnecting devices and passive components - Fibre optic connector interfaces - Part 7-3:
Type MPO Connector Family
4. IEC 61755-3-31:2015 Fibre optic interconnecting devices and passive components
5. IEC 61753-1:2018 © IEC 2018 Fibre optic interconnecting devices and passive components - Performance standard – Part 1:
General and Guidance
6. IEC 61300-3-4. Edition 3.0 2009-01 Fibre optic interconnecting devices and passive components – Basic test and measurement
procedures – Part 3-4: Examinations and measurements – Attenuation of random mated connectors
7. Telcordia Technologies Generic Requirements for Multi-Fiber Optical Connectors GR-1435-CORE
8. The Importance of Proper Cleaving for Fiber Optic Connectors, SENKO Application Note, Released Date: February 24th, 2022
9. The Relationship between Insertion Loss and Premium Ferrules, SENKO Application Note, Released Date: February 26th, 2021
10. Meticulous Research publication “Evolution of Optical Transceiver Technologies in the Last 25 Years”
www.meticulousresearch.com/blog/207/evolution-of-optical-transceiver-technologies-in-the-last-25-years, January 31, 2023
11. U.S. Bureau of Labor Statistics https://www.bls.gov/

Biography
Andrei Vankov, is an Application Engineer at SENKO Advanced Components. He received his BS from Thomas Edison
State College and his MSEE from Pennsylvania State University. He began his career in 1993 at Sumitomo ElectricLightwave Corp as a Fiber Optic Manufacturing Engineer where he worked on active and passive components using
Kaizen methods in Yokohama, Japan. As a Senior Optical Design Engineer in Franklin, MA (founded as Advanced Interconnect) Andrei Vankov developed various passive optical components and packaging integration to meet Telcordia
industry standards. He designed optical interconnects, including optical backplanes (MTP, HBMT, PHD, OGI), and afiber optic SMPTE compatible Broadcast Connector for HD applications. In 2013-2020 Andrei worked at Nokia division Radio Frequency Systems (RFS) where he provided leadership for an LTE RAN launch project team. Andrei holds
several US and European Patents in fiber optics interconnect technology.

27

THE IMPORTANCE OF LOW LOSS MPO AND SN-MT CONNECTIVITY IN TODAY’S AND FUTURE NETWORKS