100G Single-Mode Modules for Short Distance Transmission

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 As bandwidth demand continues to grow,
network service providers are looking at 100G Ethernet network to accommodate
the constant traffic surge. This new technology translates into greater speeds
and a possible network infrastructure upgrade to compensate for various
challenges that do not apply to slower networks, such as 10G, or 40G. 100G
Ethernet provides high-speed connectivity while protecting current network
infrastructures that requires broad expertise and wide-range testing to qualify
the state of the fiber, perform fiber characterization and assess the integrity
of data transmission over long-haul and ultra-long-haul networks. In response
to 100 Gigabit Ethernet, many famous telecommunication companies, like Cisco,
have delivered industry-leading, standards-compliant, 100G pluggable
transceiver modules, such as single-mode QSFP-100G-LR4 for the transmission
distance up to 10 km and multimode QSFP-100G-SR4 for the transmission up to 100
m. How about single-mode 100G modules for the transmission distance less than 2
km? Today, we’re going to introduce two 100G interfaces over single-mode fiber
for short distance transmission: 100GBase CWDM4 and 100GBase PSM4.

 

The Development History of 100GBase
CWDM4 and 100GBase PSM4

The IEEE standardized a cost-effective
100m solution known as “SR4”. Beyond 100m, there is only the “LR4” standard,
which is targeted to achieve 10km. Customers, particularly hyperscale data
centers are looking for solutions up to 2 km. To response, in 2014, a new
industry group CWDM4(coarse wavelength division multiplexed 4x25G multi-source
agreement) MSA which is consisted of Avago Technologies, Finisar Corp, JDSU,
Oclaro, and Sumitomo Electric, announced the formation of an industry
consortisum dedicated to defining specifications and promoting adoption of
interoperable 2km 100 interfaces over duplex single-mode fiber, which smooths
the process of getting to 100Gb Ethernet.

 

Like the development history of 100GBase-CWDM4,
in order to fill the requirement of low-cost 100G connections at reaches of 500
m in applications that fall in between the IEEE standardized multi-wavelength
10-km 100GBase-LR4 single-mode approach and its multimode-fiber based
100GBase-SR10 short reach specification, six technology vendors aim to promote
the creation and adoption of parallel single-mode 4-lane (PSM4) approach to
100G in the data center.

 

Main Features of 100GBase-CWDM4 and
100GBase-PSM4

100GBase-CWDM4: 100GBase CWDM4 module
comply with the requirement of CWDM4 MSA. It is a 100G optical module using
CWDM (coarse wavelength division multiplexing) technology with 4 lanes of
25Gbps optically multiplexed onto demultiplexed from a standard duplex G.652
single-mode LC or SC fiber for the link length from 2 meters to at least 2
kilometers. Transceiver modules compliant to CWDM4 MSA specification use a
color code to indicate the application. The color code can be on a module bail
latch, pull lab, or other visible feature of the module when installed in a
system The image below shows the working principle of 100GBase-CWDM4.

 

100GBase-PSM4: 100GBase-PSM4 is a
parallel module which provides increased port density, offering four
independent transmit and receive channels, and each channel operates at 25Gbps,
resulting in an aggregate data rate of 100Gbps for optical communication
applications. It can support the link length up to 500 m over single-mode MPO
or MTP fiber. The working principle of 100GBase-PSM4 is shown below.

 

Which One Is More Cost Effective?

From an optical transceiver module
structure viewpoint, PSM4 can be more cost effective, this comes in two
reasons: One is that it uses a single uncooled CW laser which splits its output
power into four integrated silicon modulators, the other is that its
array-fiber coupling to an MTP connectors is relatively simple.

 

However, from an infrastructure
viewpoint, PSM4 would be more expensive when the link distance is long, mainly
due to the fact that PSM4 uses 8 optical single-mode fibers, while CWDM4 uses
only 2 optical single-mode fibers.

 

When take these two factors into
considerations, a total cost comparison can be qualitatively shown in the
figure below. As can be seen in the figure, PSM4 starts with a lower cost due
to its lower transceiver cost, but as the link distance increases, its total
cost climbs up very fast due to the fact that it uses 8 optical fibers.
Besides, if deploying PSM4 modules, the entire optical fiber infrastructure
within a data center, including patch panels, has to be changed to accommodate
MTP connectors and regular single-mode fiber cables. In addition, cleaning MTP
connector is not a straightforward task.

 

Conclusion

With the requirement for longer
distances and higher data transmission speed increases, 100GBase-CWDM4 and
100GBase PSM4 which provide lower-cost, lower power option for what can be
referred to as medium-reach distances that is future-proof for the next
generations of data transmission speeds. fiber-mart.COM offers compatible
100GBase-CWDM4 and 100GBase-PSM4 for many brands at affordable price. You can
choose the right one according to your need.