Low-loss bend-resistant optical fiber helps future network construction

Optical fiber is the cornerstone of modern communication networks, providing data capacity and conduction rates that enable the latest communication devices and services
.
As network demands rise, so do the demands placed on fiber: greater capacity, faster speeds, and greater adaptability
to configurations.
Due to the growing data capacity and relatively sluggish revenue of the telecom industry, operators need to make effective capital expenditures on the network and achieve low cost (OAM) in operation, management and maintenance to support the return on
investment of the telecom industry.

To this end, operators adopt an optical transport network (OTN) approach that enables different service types (e.
g.
, SONET/SDH, Ethernet, optical channel, and storage services) to coexist at the same transport layer
.
The versatility of this protocol transport and the transparency of the service results in significant capital expenditures and OAM benefits for operators, ultimately reducing the cost
per bit of optical transport.

Similarly, operators are looking to system vendors to provide networks with greater capacity and control per-bit optical transmission costs
.
In order to expand the transmission capacity, the data transfer rate is increased
.
However, each step increase in data transfer rates puts pressure on system tolerances, and while this pressure has so far been offset by the increased complexity of optoelectronic systems, it is important to know that system complexity is inherently synonymous
with increased cost.

However, the foundation of the network, fiber optics, can help solve this
problem.
At the first two main transmission wavelengths, 1310nm and 1550nm, the attenuation of optical transmission is significantly reduced to 0.
35dB/km and 0.
21dB/km, respectively, while the signal strength at the receiver is also improved
.
The now commercially available low-loss standard single-mode fiber G.
652.
D exhibits excellent transmission low loss of 0.
32 dB/km and 0.
18 dB/km at 1310nm and 1550nm wavelengths
, respectively.
The result is improved system tolerance, reduced system complexity and transmission cost
per bit.

With the adoption of high-speed broadband, operators are seeking similar cost-per-bit efficiencies
in access networks.
We have seen that large-scale overhead layings and space-constrained connector boxes can cause signal loss and reduced system tolerances when the fiber optic cable is bent
.
Therefore, in order to protect tolerances and reduce OAM costs for network access, low bending loss fibers were developed and classified into the ITU-T G.
657 standard
.
G.
657 fiber contains three main classifications:

G.
657.
A1, bending performance improvement fiber; G.
657.
A2, bending performance enhanced fiber; G.
657.
B3, bending performance insensitive fiber
.

Among the three types of optical fibers, G.
657.
A1 is the most commonly used optical fiber
for outdoor cables.
G.
657.
A2 and G.
657.
B3 fibers with excellent bending properties are not necessary for outdoor equipment conditions; In addition, the superior bending performance produced by the core cross-section process of these two optical fibers is not compatible
with the field welding and installation of high-volume outdoor equipment basically using G.
652D fiber.

Due to the emergence of low-loss optical fibers and bend-resistant optical fibers, how to use these two optical fibers separately in suitable scenarios has become a technical challenge for network designers
.
In order to maximize economic benefits, network designers have to carefully select two kinds of G.
652.
D fiber and G.
657.
A1 fiber in different parts of the network system, which also means the need
for fiber optic cable diversity.
Therefore, change becomes inevitable
.

New era

If the construction personnel no longer need to choose which kind of fiber, or in other words, there is no need to choose between low-loss or bending low-loss fiber, the wiring of optical fiber cables will be much
simpler.
The advanced nature of the newly developed optical fiber makes people no longer bother
with such a choice.
The latest generation of G.
652.
D fiber brings the industry's most cutting-edge low-loss performance and improves the bending resistance of G.
657.
A1 fiber, while also satisfying forward compatibility
.

The new fiber has a low loss of 0.
18dB/km at 1550nm and 0.
32dB/km at 1310nm wavelengths (which also allows the average loss of the cable to be on the same reference).

Its bending resistance exceeds the standard of G.
657A1, and the mode field diameter of 9.
2 microns also matches the early G.
652D fiber
.
Results: Adequate system tolerance for high capacity; Improved flexurality to adapt to access networks and reverse compatibility with earlier G.
652.
D fibers, all thanks to a small fiber
.
To better understand what such a fiber can bring to operators, let's take a closer look
.

The advantages of low transmission loss are obvious

As data rates increase from 10 Gbps to 40 Gbps and then to 100 Gbps over long distances, systems need to achieve higher optical signal-to-noise ratios
through the use of advanced modulation formats, coherent industrial techniques, and digital signal processing.
However, at 100 Gbps, this implementation is reduced
due to the lack of optical signal-to-noise ratio.

The transition to 400Gbps will put further pressure on system implementation, as in the transition to an all-optical network, where optical add-drop multiplexers and optical switches increase the average length of the connection, which also means additional losses
for components in the network.

Low-loss fiber optic networks have spread across the globe, and increasing optical signal-to-noise ratios offer many benefits:

Achieve higher transmission rates with minimal distance sacrifice; Reduce the number of amplifications in long-distance transmissions; By providing additional system redundancy for OADMs, which simplifies the transition to all-optical networks, indirect economic benefits of low-loss fiber performance have also been proven
.

Low-loss optical fiber also invisibly prolongs the repair and use cycle
of optical cables.
In some developing countries, the pace of new transport and infrastructure development has led to frequent cable breaks
.
Without sufficient redundancy of the cable, this cable will soon be obsolete and some cables will only be used for 5 years, as frequent maintenance depletes the system's power budget, in stark contrast
to the market expectation of 20 years or more for fiber optic cables.

In the access network, these new low-loss fibers can extend FTTx and mobile backhaul systems, and can extend coverage to 20% of users, buildings (at 1310 nm, low-loss fibers have only 0.
32 dB/km loss compared to 0.
35dB/km loss).

Additional tolerances not only extend the life cycle of the cable, but also use pre-connected solutions to make cabling more efficient
.

The systematic evolution of network access will see GPON coexisting
with the new 10Gbps XGPON standard.
To achieve this, the XGPON upstream wavelength was reduced from 1310 nm to 1270 nm, which is inherently higher transmission loss
than 1310 nm.
When XGPON is deployed on a traditional GPON network, the additional loss of upstream wavelength challenges system tolerances and the original system design in terms of extension and coverage
.
However, the transmission loss of advanced G.
652.
D low-loss optical fiber at 1270nm wavelength is almost the same as that of traditional G.
652.
D at 1310nm wavelength
.
This feature will allow the original system design to complete the upgrade
from GPON to XGPON with minimal effort.
Similarly, WDM-PON may be able to use higher attenuation wavelengths of more than 1600 nm, and therefore benefit from low-attenuation fibers
.

Low bending loss improves transmission performance

The demand for high-speed broadband services is driving the penetration of optical fiber in access networks to provide FTTx broadband services and 3G and 4G wireless broadband data backhaul services
.
Fiber optic cables present different challenges in laying these networks, which can be accomplished by G.
657 fiber with low bending loss
.
The particular challenges facing access networks are varied
.

The outdoor access network is essentially a distributed network with many nodes that manage the connection system with fiber management, such as computer rooms and connector boxes
.
Due to space constraints and space aesthetic requirements due to high population density, the space in these machine rooms and connector boxes needs to be very compact
.

The optical cables connected to the building, residents and 4G antennas are usually laid overhead, and these overhead cables need to be lightweight and flexible
.

User density and limited usable space have promoted the design of outdoor cable diameters with smaller outer diameters, and large-core optical cables that can increase the capacity of the access network have become a general trend
.

All of these factors in the access network pose challenges
to the bending resistance of fiber optic cables.
Fiber optic cables are subject to smaller bending radii
when connected to machine rooms or connector boxes where space is tight.
Overhead cables, on the other hand, need to cope with flexible laying and high and low temperature changes
during the life cycle.
In order to reduce signal loss caused by bending and the bending performance and low temperature resistance of overhead optical cables, the bending resistant G.
657.
A1 optical fiber has been used in the access network
.
On the other hand, small diameter, large core count optical cables will cause micro-bending stress on the internal optical fiber, resulting in optical signal loss
.
Therefore, optical fibers with improved bending resistance are used in these small-diameter, large-core network access cables, which contribute to the improvement
of optical signal loss.

Just as the telecommunications industry is full of exciting changes and new devices for consumers, the world of telecom operators is full of challenging changes and new network capacity upgrade requirements—all of which require low investment and low-cost maintenance to guarantee a good return on network investment
.
Therefore, operators around the world are laying optical transmission networks, and through the good interoperability of OTN networks, building a low-cost and high-efficiency convergence long-distance trunk line, metro area and access communication network
.

Now, these operators can further benefit from their fiber infrastructure, as people no longer need to choose
between bend loss improvements and advanced low-loss performance.
Now, both functions are available
in a single fiber.
This fiber simplifies cabling design, reduces costs, and increases capacity to accommodate future long-haul trunk, metro and access network construction
.