Loss and Dispersion Compensation

  • Description

    The placement of amplifiers, attenuators, and dispersion compensating elements (DCMs) has to be done to keep the link performance, optical powers, accumulated dispersion, and OSNR within the equipment capacity (Figure 1). Besides, design engineering rules impose extra limitations on system performance.
    The Design Assistant mode simplifies and accelerates the tedious routine of manual equipment configuration, especially of complex WDM networks. It shows problem points, lists equipment that can be inserted, and simplifies configuration process.
    The compensation process includes several steps:

    • Validation of the initial configuration (Do all channels meet receiver operating ranges? Are amplifiers and DCMs required?

    • Placement of amplifiers and DCMs taking into account input signal metrics, design rules constraints, and equipment operating ranges

    • Placement of attenuating pads to equalize added and express channels or to attenuate dropped channels to meet receiver limits

    • Evaluation of system performance during the design process

    • Placement of amplifiers and attenuators at ring break points in order to finalize manual link loss compensation in the design with simulation feedback

    The system design workflow also includes detailed performance analysis and report generation using the built–in functionality of VPIlinkConfigurator or customized reporting tools realized via API.

  • Typical Results

    This application example demonstrates key steps of the manual equipment configuration in a simple ring design through the use of the Design Assistant mode:

    • Problem area notification simplifies validation of WDM system configuration. Violations of equipment limits and design rule constraints for a selected transmission line are reported in a summary table (Figure 2).

    • Based on design rule constraints, the Design Assistant validates available equipment against the input signal and lists the equipment that can be inserted before the selected item. If an attenuating pad is required, it is added automatically before the inserted amplifier or DCM (Figure 3).

    • Variable optical attenuators (VOA) required to equalize added and express channels or to attenuate dropped channels to meet receiver limits are calculated automatically. Thus, power balancing at the add/drop stage can be done in one click (Figure 4 and Figure 5).

    • Recalculation of signal metrics and the validation of signal power, accumulated chromatic dispersion, and OSNR for each optical channel against system requirements and equipment capacity is done automatically at each design refinement step. The summary table and signal metrics charts are instantly updated to let you track the design progress (Figure 4 and Figure 5).

    • To finalize manual link loss compensation, amplifiers and attenuators are added at ring break points to have the same power level at input and output ports of the auxiliary components that set Target Power level. For example, 18 dB gain is required to meet the target power level at one of the break points (Figure 6). As only 13dB and 21dB amplifiers are available, the attenuating pad after the amplifier should also be added along with a 21dB amplifier.

    Once the equipment placement is done, the simulation engine should be switched to the Iterative mode to see whether all design rule constraints and equipment limits are met (Figure 7).

  • Possibilities

    An Application Programming Interface (API) of VPIlinkConfigurator lets you create design automation tools to account for design constraints and operating ranges of equipment available for a design and to generate a set of solutions optimized with respect to equipment cost and performance metrics (Figure 8 and Figure 9). Automated equipment configuration is a welcome alternative to manual link loss and dispersion compensation.

  • Further Information

    Keywords: Optical Mesh Network Design, Optic Loss Budget, Fiber Attenuation, EDFA, Accumulated Chromatic Dispersion, DCM, Optical Receiver Sensitivity, DWDM System Performance, Receiver Margins, Design Automation, Scripting

    See also the Third Party Software Interface application example for more information about the VPIlinkConfigurator API.

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