Bandpass Filter Module for Selectable Wavelength Access in AWG-Based PON

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Solution Overview

Problem

Conventional AWG-based WDM PONs lack flexibility in assigning OLT transmitters to ONUs, limiting open access and requiring additional cost and complexity for reconfigurable solutions or fully tunable transmitters.

Innovation Solution

An optical network unit (ONU) with a bandpass filter module coupled to an arrayed waveguide (AWG) allows selection of AWG cycles for downstream and upstream transmission, enabling flexible access to multiple OLTs and services without the need for reconfigurable optical add-drop multiplexers or fully tunable transmitters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional AWG-based WDM PON is used with fixed wavelength mapping, then device complexity is reduced, but adaptability and network flexibility are limited

Engineering Contradiction:

Improvenetwork flexibilityVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements dynamic wavelength assignment by allowing ONUs to be assigned to different AWG cycles (spectral windows) on demand. The system dynamically reconfigures which wavelengths are assigned to which ONUs based on service requirements, enabling flexible adaptation without changing the physical AWG connectivity. This resolves the contradiction by providing adaptability through dynamic software-controlled wavelength assignment rather than through complex reconfigurable hardware.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If reconfigurable optical add-drop multiplexer or fully tunable transmitters are used, then adaptability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveopen access capabilityVSAvoidoperational complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent changes the operational parameters (wavelength assignments and AWG cycle allocations) through software control rather than through complex reconfigurable hardware. By dynamically adjusting which wavelengths are assigned to which ONUs and which AWG cycles are allocated to which OLTs, the system achieves open access capability without requiring costly reconfigurable optical add-drop multiplexers or fully tunable transmitters. This resolves the contradiction by providing adaptability through parameter reconfiguration rather than hardware complexity.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple OLTs serve the same ONU, then adaptability is improved, but wavelength interference and signal conflict increase

Engineering Contradiction:

Improvemulti-provider accessVSAvoidwavelength interference

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the wavelength spectrum into multiple AWG cycles (spectral windows), with each cycle allocated to specific OLTs. This segmentation allows multiple OLTs to serve the same ONU simultaneously on different wavelength cycles without interference. For example, OLT 112 and OLT 114 can both serve ONU 122 on different AWG cycles. This resolves the contradiction by providing multi-provider access through spectral segmentation rather than through wavelength sharing that would cause interference.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution enhances network flexibility and cost-effectiveness by allowing ONUs to access multiple services and providers, increasing network capacity and reducing operational complexity while maintaining compatibility with existing AWG-based infrastructure.

Implementation Method 1

A WDM PON can incorporate an arrayed waveguide (AWG) within its ODN. When laser light enters an AWG from a single fiber, the laser light is de-multiplexed into multiple separate wavelengths with each wavelength exiting a port of the AWG.

Methodology Applied

Scientific EffectWavelength division multiplexing:

Implementation Method 2

The ONU receives downstream signals from a first plurality of OLTs through a designated port of the AWG and a bandpass filter module coupled to the designated port. The bandpass filter module is adapted to select any one of the first plurality of AWG cycles at a given time.

Methodology Applied

Scientific EffectBandpass filtering: Filter (optical)

Data Source

PatentUS8855492B2Selectable multiple-wavelength access for optical network units in arrayed waveguide based wavelength division multiplexing passive optical network

Publication Date: 2014.10.07 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

An optical network unit (ONU) accesses services provided by multiple optical line terminals (OLTs) in a wavelength division multiplexing (WDM) passive optical network (PON). The ONU receives downstream signals from a first plurality of OLTs through a designated port of an arrayed waveguide (AWG). At any given time, the bandpass filter module can select any one of a first plurality of AWG cycles allocated to the first plurality of OLTs. Based on received downstream signals, the ONU transmits upstream signals to a second plurality of OLTs through the designated port of the AWG. At any given time, the bandpass filter module and a transmitter of the ONU can select any one of a second plurality of AWG cycles allocated to the second plurality of OLTs. The ONU may be configured with a plurality of receivers and transmitters, whereby it is enabled to simultaneously subscribe to a plurality of AWG cycles.