OTN Emerges for Metro Transport Networking - Light Reading

OTN Emerges for Metro Transport
Networking
Huawei metro OTN delivers SDH-like configuration, simplified O&M, enhanced service support, and large granularity
access.
Metro network challenges
Most metro transport networks currently use fiber to directly connect Internet routers. As bandwidth speeds accelerate
and streaming media services grow and diversify, five challenges are making themselves felt:
Increased fiber costs
Web browsing and email are intermittent and consume modest bandwidth; their network convergence ratio can reach
16:1. Video service, on the other hand, is an uninterruptible bandwidth hog; it reduces the convergence ratios
between OLT/DSLAM and BAS, and between BAS/SR and CR, while the network layers can be reduced from five to
three.
To flatten the network, a large number of GE/10GE ports need direct (and possibly multiplied) fiber connections
between the OLT/DSLAM and BRAS, and between the BRAS/SR and CR, but pipe/cable laying costs in urban areas are
increasing.
Inflexible configuration
As service categories mushroom and bandwidth increases, different types of ports may be used between the
aforementioned network elements. For example, an OLT may use GE ports while a BRAS provides 10GE ports. In this
case, the upstream equipment needs to adapt to the downstream ports, reducing the former’s access capability.
Although 40G ports are being widely used on the metro core network, 40G POS ports support a short transmission
distance and cannot meet the requirements for interconnected CRs, making 40G ports, and 100G ports (which have an
even shorter range), unsuitable for direct fiber connection scenarios.
Long project delivery duration
If direct fiber connection is used for E2E services, the engineering workload is multiplied in terms of site survey, fiber
splicing, ranging, and cable jumping. Furthermore, two routes are usually configured for direct data device
transmission. When one optical route fails, route selection for the other may require complex ranging and fiber splicing
for multiple fiber distribution tables (FDTs). A fault in any cable section along the route may deteriorate line quality.
When devices are directly connected using optical fiber, network delivery duration is extended, making for a bottleneck
in service delivery/response.
Difficult line management
Currently, OLTs are widely distributed across access-layer equipment rooms in certain cities. In a moderately developed
city, if the number of broadband users reaches 1.2 million, at least 500 OLTs are typically required, spanning nearly
1,000 equipment rooms. Said OLTs provide roughly 8000 GE ports and require 16,000 optical fibers for BRAS
connection, while 17,000 fibers are required between CRs and between BRASs/SRs and CRs. These optical fibers and
cables may traverse multiple FDTs and optical distribution frames (ODFs), which means that tens of thousands of lines
and multiple ODFs will be involved in maintenance. However, efficient monitoring and troubleshooting measures are
currently unavailable, making fault location time consuming and less accurate.
Difficult network evolution
Fiber connection for equipment can only be done point-to-point, which means that E2E transmission is impossible, as
1 HUAWEI TECHNOLOGIES CO., LTD.

there is no network transport platform, while plug-and-play functionality, service evolution, capacity expansion, and
multiple service protection are hardly available.
Metro OTN is emerging
These challenges are driving many operators to simplify their OAM and upgrade their hardware, architecture, and
services for metro OTN, which is currently being moved from the metro core layer to the convergence and even the
access layer, enabling ultra-broadband service support. However, OTN network usage and OAM efficiency can be
improved in the following areas:
Simplified OTN deployment
Many elements are involved in metro OTN planning and deployment, including wavelengths, OSNR margins, chromatic
dispersion (CD) compensation, and polarization mode dispersion (PMD) compensation; simplifying them would ease
network planning and deployment remarkably.
Huawei has developed an intelligent OTN planning tool that greatly accelerates the process. Fiber connections and
optical/electrical-layer configurations can be shared between this tool and the Huawei NMS, freeing engineers from
the chores of complex planning and computation. For service configuration at multiple layers that span the client,
ODUk, OTUk, OCh, OMS, and OTH, engineers need only create OCh and client services using the NMS, as services at
the other layers will be automatically delivered by the NMS, reducing service provisioning time by 60%.
Moreover, Huawei also offers an innovative optoelectronic integrated chip (PID) solution where each PID port outputs
200G traffic, enabling this solution to use an SDH-like design and PDI-line boards with different specifications to meet
different transmission distances, eliminating the need for complex wavelength planning, board selection, OSNR
calculation, and OA board computation.
End-to-end OTN network OAM
Metro OTN networks require end-to-end OAM capabilities similar to those for SDH networks. Huawei's metro OTN
networking supports resource usage statistics at the electrical layer (especially the ODU1/2/3 layer of the OCh) and the
optical layer between WDM NEs, while also supporting client-side port resource statistics, facilitating the clear display
of resource usage status, and performing expansion planning.
Bidirectional WDM trails on OTN networks must be connected to prevent residual cross-connections when a channel is
deleted. OTN networks should be monitored in terms of optical-layer network performance, end-to-end OAM for
cross-connections, wavelengths, sub-wavelengths, and Ethernet services. Huawei's metro OTN supports Layer 2
features similar to those for Ethernet data services, greatly reducing the time spent on onsite maintenance.
With Huawei OTN networking, regeneration boards are configured for each PID site; this SDH-like design enables
timely fault location, while PID sites require only standard maintenance skills, meaning that they can be maintained by
regular SDH engineers.
Huawei's metro OTN solutions can help operators boost their network operations, thanks to a number of enhanced
features such as PID and OTN integration, expanded OTN cross-connection, and simplified OTN planning and O&M.
2 HUAWEI TECHNOLOGIES CO., LTD.