This chapter introduced the Cisco ONS 15454 Multiservice Transport Platform (MSTP). It detailed the common and interface cards that comprise the ONS 15454 MSTP system, including the purpose for which each card is used in the MSTP system. The ONS 15454 allows for flexible deployment of either TDM/Ethernet or DWDM services. For the DWDM application, a wide variety of fixed-channel optical add/drop units are available for services delivery. However, the most flexible aspect of the ONS 15454 MSTP resides in its ROADM capability. ROADM deployments provide many benefits to DWDM networks, among them reduced equipment-
This chapter and
Additionally, the ONS 15454 MSTP service capacity is being enhanced with new 10-Gbps transponder/
Chapter 10. Designing ONS 15454 MSTP Networks
The design of dense wavelength-division multiplexing (DWDM) networks can
This chapter is not intended to provide a complex, thorough analysis of DWDM fundamentals. It is assumed that the reader has a basic knowledge of DWDM transmitters, receivers,
ONS 15454 MSTP DWDM Design Considerations
In general, DWDM designers and planners must be cognizant of several factors that influence system topology and transmissions capability. Among them are physical limitations, such as structure locations, and fiber plant type. Additionally, the system bandwidth requirements and scale should be taken into account, along with the DWDM equipment limitations such as
For existing DWDM deployments, physical structure locations are usually already predetermined for amplifier/regenerator locations. For example, existing DWDM systems may use 60 km amplifier spacing rules; thus, because outside plant enclosures and power are already present at these locations, it is prudent for the DWDM designer to engineer the new system within the present amplifier spacing rules. The drawback associated with using existing structures and spacing is that it might be economically inadvisable or systematically
In addition to physical structure requirements, when providing DWDM over existing fiber infrastructure, the design is usually constrained by the transmission characteristics of the existing optical fiber. Essentially, three types of fiber are used today: standard,
Figure 10-1. Optical Fiber Performance Profile
From an attenuation standpoint, DWDM C-band and L-
Figure 10-2. Wavelength Signal Broadening Caused by Chromatic Dispersion
The DS-fiber mitigates this issue by shifting the zero-dispersion parameter from the 1310 nm region to the 1550 nm region. This facilitates long-distance, high-bit-rate transmission for a single wavelength at 1550 nm because only optical attenuation is a signal-
Certain fiber anomalies, such as FWM and channel cross-talk, are offset by the chromatic dispersion effect. However, if the signal
Thus, to increase channel capacity from 2.5 Gbps to 10 Gbps (a fourfold increase), chromatic dispersion tolerance decreases by a factor of 16.
Many other fiber-transmissions factors must be
The effect of other fiber nonlinearities, such as stimulated brillion scattering, stimulated raman scattering, cross-phase modulation, and self-phase modulation also must be taken into account when designing DWDM systems; however, these effects can be controlled with proper equipment design.
Amplified systems present their own complexities in terms of optical signal-to-noise ratio (OSNR) and channel gain tilt. For example, when engineering each amplified span, the DWDM engineer must compute the OSNR between each span to ensure that the signal level is within receiver specifications for each amplifier in use. The following formula is used for OSNR measurement for a multistage amplifier:
As you can see, manually computing the effects of each fiber transmission effect for each span/wavelength set can be a cumbersome task. For this reason, the ONS 15454 MSTP is broken into a set of design rules for each topology type. The design rules take into account the limitations of each optical component used within the system so that the DWDM engineer need only compute the optical fiber limitations, which vary from span to span.