September 2024 Vol. 22 No. 992024

https://www.ntt-review.jp/Kei Ikeda, Senior Vice President, Head of Technology
Planning, NTT Corporation▼Abstract

Kunio Kashino, NTT Fellow, NTT Communication
Science Laboratories

Rising Researchers
Makoto Nakatsuji, Distinguished Researcher, NTT
Human Informatics Laboratories

Feature Articles
Challenging the Unknown: Mathematical Research and Its Dreams
A Mathematical World Woven by Number Theory, Algebraic Geometry, and Representation
TheoryArithmetic Problems in Dynamical Systems
How Number Theory Elucidates the Mysteries of Complex Dynamics—Viewed throughNon-Archimedean Dynamics
Motives—Abstract Art of Numbers, Shapes, and Categories
Representation Theory and Combinatorics Arising from Determinants
Symmetry and Representation Theory of Lie Groups and Lie Algebras
Modular Forms and Fourier Expansion
Light-matter Interaction and Zeta Functions

Regular Articles
Digital Longitudinal Monitoring of Fiber-optic Link Using Coherent ReceiverCollaborative Business Navigation Platform That Comprehensively Supports Work of Operators
Work-improvement-support Technology that Supports Wide-ranging Implementation andApplication of Digital Transformation Measures

Global Standardization Activities

Feature Articles
Challenging the Unknown: Mathematical Research and Its Dreams

A Mathematical World Woven by Number Theory, Algebraic
Geometry, and Representation Theory▼Abstract
Through basic research in mathematics, theNTT Institute for Fundamental Mathematics
aims to enrich the “fountain of knowledge” that
nourishes science and technology. In thisarticle, we first provide an overview of theresearch being carried out at the Institute thenintroduce the Institute’s core research areas:
number theory, especially arithmetic dynamics;
algebraic and arithmetic geometry; andrepresentation theory and automorphic forms.

FA2: Arithmetic Problems
in Dynamical Systems

Dynamicalsystem

FA3: How Number Theory
Elucidates the Mysteriesof Complex Dynamics—
Viewed through NonArchimedean Dynamics

p-adic field

NumberTheory

Algebraic geometry
Arithmetic geometry
Topology

Measure theory
Probability theory

Fourier analysis
Differential equation

FA8: Light-matter
Interaction and Zeta
FunctionsFA5: Representation Theory
and Combinatorics Arisingfrom Determinants

Representation
TheoryModular forms
Elliptic curves

Lie group
Lie algebra

FA4: Motives—Abstract
Art of Numbers, Shapes,
and Categories

FA7: Modular Forms
and Fourier Expansion

FA6: Symmetry andUnitary representation Representationdifferential equation
Theory of Lie Groupsand Lie Algebras

Elliptic curves

Graph theory, combinatorics

Regular Articles

Digital Longitudinal Monitoring of Fiber-optic Link Using
Coherent Receiver▼Abstract
In fiber-optic communication systems, it is
crucial for operators to accurately monitor
various physical parameters along optical links
to fully leverage the potential transmission
capacity and conduct fault analysis. Digital
longitudinal monitoring (DLM) has been
intensively studied for its capability of monitoring
various physical parameters, such as opticalpower, distributed along the fiber-longitudinal
direction by solely processing signals received
at coherent receivers. In this article, thefundamentals and recent advances in DLM arereviewed, including working principles, spatialresolution, and key experiments demonstrating
its feasibility for use in operations.

Optical filter

Optical filter
Rx DSP

TxDLM

Optical fiber• Fiber-longitudinal power profile• Span-wise CD• PDL localization• Multi-path interference

Optical amplifier• Gain spectra and tilts• Optical link tomography (spectral andspatial power profile)• Raman-amplified power profile(a) Fiber-longitudinal power profile(b) Optical link tomography

Optical filter• Frequency responses(passband narrowing)(c) Filter response separation
15Freq. response(dB)

Front-line Researchers

EstimatedPower (dBm)

Kei Ikeda, Senior Vice President, Head of Technology
Planning, NTT Corporation

The NTT Group is committed to solving social issues as a leading corporate groupin the telecommunications business with a public responsibility. Its goal is to create
a well-being society by building the world’s most-advanced and sustainable social
systems and infrastructures. We interviewed Kei Ikeda, NTT senior vice president,
head of technology planning, who also serves as the co-chief artificial intelligence
officer and chief information officer, about the NTT Group’s technology strategies
and his beliefs as a top executive.

EstimatedPower (dBm)

View from the Top

ITU-T SG16 Meeting Report

View from the Top

0−5−10−15050
Distance (km)105Distance (km)Frequency (THz)

PBN detection

0−5100

1st optical filter (0 GHz shift)
2nd optical filter (+15 GHz shift)−60 −40 −20 0
20 40
Frequency (GHz)60