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Internet data transmission speed record set by scientists using optical cables

Data traffic is increasing at a rapid pace, and this necessitates the development of smaller optical transmitters and receivers capable of high-order multi-level modulation and faster data transmission rates.

Addressing this need, researchers have created a new compact indium phosphide (InP)-based coherent driver modulator (CDM) that surpasses others in terms of baud rate and transmission capacity per wavelength.

Revolutionizing optical data transmission

CDMs are crucial components of optical communication systems as they encode information onto light by modulating its amplitude and phase before transmission through optical fibers.

Josuke Ozaki from NTT Innovative Devices Corporation in Japan emphasizes the importance of optical transmission systems with increased data rates in enabling services like video distribution and web conferencing.

“Services that require data capacity, such as video distribution and web conferencing services, have become widespread, and services that more enrich our lives are expected to be introduced in the future,” said Ozaki.

The lack of sufficient optical transmission capacity poses challenges in realizing new convenient services and building a data-driven society.

Astounding potential of new optical transmitter

An additional benefit of the development of an optical transmitter that covers the C+L band in a single module is the promotion of flexible network operation and reduced equipment costs.

Ozaki will present these impressive results at OFC, a premier global event for optical communications and networking scheduled to take place as a hybrid event from 24 – 28 March 2024 at the San Diego Convention Center.

The baud rate, which denotes the number of signal changes occurring in a communication channel per second, serves as a measure of data transmission speed.

Higher baud rates require increased bandwidth for each modulation signal, resulting in fewer channels transmitted in the conventional C-band.

Therefore, extending the wavelength bandwidth from the C-band to the L-band, collectively known as the C+L band, becomes imperative.

InP modulator chip enables high-speed data transmission

Modulators made from the InP semiconductor exhibit excellent optical and radio frequency characteristics.

However, these modulators have faced challenges in extending their wavelength range due to strong wavelength dependence.

Researchers have overcome this obstacle by developing an innovative InP modulator chip featuring an optimized semiconductor layer and waveguide structure capable of operating over a wide range.

Utilizing this novel modulator chip, they achieved the world’s first CDM with an InP modulator chip that can transmit in the C+L band. Remarkably, the package body measures just 11.9 × 29.8 × 4.35 mm³.

Operating in the C+L band, the new CDM exhibited an electro-optic 3-dB bandwidth exceeding 90 GHz, insertion loss at maximum transmission below 8 dB, and an extinction ratio of 28 dB or more.

Unveiling the power of InP modulator chips

To demonstrate the capabilities of the new CDM, researchers conducted experiments using 180 Gbaud probabilistically constellation-shaped 144-level quadrature amplitude modulation (PCS-144QAM) signals.

The results were astonishing, with a net bit rate of 1.8 Tbps (terabytes per second) achieved over an 80-kilometer standard single-mode fiber in the C+L band.

This marks the first demonstration of an InP-based CDM operating in the C+L bands and sets a world record for transmission capacity per wavelength in a CDM.

Alpha samples of the CDM are now ready for shipping from the NTT Innovative Devices Corporation.

According to Ozaki, the next step is to further increase the baud rate to achieve even higher transmission speeds.

To accomplish this, new modulator structures and assembly configurations, including a driver die and package, must be developed to achieve higher electro-optic bandwidth while reducing power consumption and form factor.

Transmission breakthrough fuels data-driven society

In summary, the development of the compact indium phosphide (InP)-based coherent driver modulator (CDM) represents a significant advancement in the field of optical communications and networking.

This groundbreaking technology, with its record-high baud rate and transmission capacity per wavelength, opens up new possibilities for data transmission in an era of increasing data traffic.

By achieving an unprecedented net bit rate of 1.8 Tbps (terabytes per second) over 80 kilometers in the C+L band, this new CDM sets a world record and demonstrates its potential for revolutionizing optical communication systems.

The research presented at OFC by Josuke Ozaki and the team showcases the immense possibilities of InP modulator chips and their impact on realizing high-speed, efficient, and reliable data transmission.

As the demand for higher data rates and improved optical transmission capacity continues to grow, the advancements made in the development of CDMs will play a crucial role in enabling future services and shaping a data-driven society.

About OFC

The OFC, a premier global event for optical communications and networking, draws attendees from across the globe to a conference and exhibition that showcases the latest industry advancements and emerging technologies.

This event provides a platform for start-ups to debut their innovations and for industry leaders to set the course for the future. An exciting series of programs and events will comprehensively cover the entire ecosystem with a focus on inclusivity.

About Optica

Optica, formerly known as OSA, is the society dedicated to advancing optics and photonics worldwide. Since its establishment in 1916, Optica has been the leading organization for scientists, engineers, business professionals, students, and others interested in the science of light.

Optica actively promotes the generation, application, archiving, and dissemination of knowledge in the field. Through its renowned publications, meetings, online resources, and in-person activities, Optica drives discoveries, shapes real-life applications, and accelerates scientific, technical, and educational achievements. To learn more, visit


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