Multidrop Optical Memory Module Using Wavelength Ring Couplers

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Solution Overview

Problem

The capacity and bandwidth of dynamic random access memory (DRAM) modules per central processing unit (CPU) are limited by the number of electrical connections, and optical fiber connections are expensive in system assembly.

Innovation Solution

Implementing a multidrop optical connection system using wavelength resonant ring couplers and modulators on buffer integrated circuits to facilitate concurrent information transmission and reception between the CPU and memory modules, utilizing different wavelengths of light on the same waveguide.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If optical fiber connections are used to increase DRAM module capacity and bandwidth, then transmission capability is improved, but system assembly cost increases

Engineering Contradiction:

ImproveDRAM module capacity and bandwidthVSAvoidsystem assembly cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

Multiple optical connections are merged into a single waveguide by using wavelength division multiplexing. Different wavelength channels are combined and transmitted through the same physical waveguide, reducing the number of separate optical fiber connections needed and lowering assembly costs while maintaining high bandwidth capacity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The waveguide structure is designed to handle multiple functions simultaneously by carrying multiple wavelength channels. Each buffer integrated circuit can both receive and transmit optical signals on different wavelengths through the same waveguide, making the connection system universal and reducing the need for separate dedicated connections

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If multiple optical connections are used to increase DRAM module capacity, then bandwidth is improved, but device complexity increases

Engineering Contradiction:

ImproveDRAM module capacityVSAvoidnumber of optical connections

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The system transitions from spatial multiplexing (multiple separate waveguides) to spectral multiplexing (multiple wavelengths on one waveguide). By adding the wavelength dimension, multiple data channels are accommodated within a single physical connection, reducing complexity while increasing capacity

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

Wavelength selective couplers and resonant ring modulators act as intermediaries that manage multiple wavelength channels within a single waveguide. These components enable efficient routing and modulation of different wavelength signals without requiring separate physical connections for each channel

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enhances the capacity and bandwidth of DRAM modules by reducing the number of optical connections and optimizing signal transmission efficiency through frequency division multiplexing.

Implementation Method 1

wavelength resonant ring couplers disposed on the buffer integrated circuits are used to separate the wavelength being received by a particular buffer integrated circuit from the wavelengths of light destined for other buffer integrated circuits on the same waveguide

Methodology Applied

Scientific EffectWavelength resonant coupling: Resonance

Implementation Method 2

Wavelength resonant ring modulators also disposed on the buffer integrated circuits modulate specific wavelengths of light unique to each buffer integrated circuit to transmit information to the CPU

Methodology Applied

Scientific EffectWavelength resonant modulation: Resonance

Implementation Method 3

a first polymer waveguide to couple the first light wave carrier into the first silicon waveguide and to receive the first light wave carrier back from the first silicon waveguide

Methodology Applied

Scientific EffectOptical waveguide coupling: Waveguide (optics)

Data Source

PatentUS12475944B2Multidrop optical input/output module

Publication Date: 2025.11.18 RAMBUS INC

AI summary

Multidrop optical connections are used for an optical memory module. Multiple buffer integrated circuits on a module each receive information from the host system using different wavelengths of light transmitted on the same waveguide. Multiple buffer integrated circuits each transmit information back to the CPU using different wavelengths of light transmitted on another waveguide. Wavelength resonant ring couplers disposed on the buffer integrated circuits are used to separate the wavelength being received by a particular buffer integrated circuit from the wavelengths of light destined for other buffer integrated circuits on the same waveguide. Wavelength resonant ring modulators also disposed on the buffer integrated circuits modulate specific wavelengths of light unique to each buffer integrated circuit to transmit information to the CPU.