Commercialization of compact thin-film LN modulator
Press Release
October 22, 2021
Fujitsu Optical Components Limited.
Commercialization of compact thin-film LN modulator
～Successful Establishment of Highly Reliable Technology～
Fujitsu Optical Components Limited (FOC) announced today that it is commercializing the world's first thin-film LN modulator (*1) of the 200GBaud class, achieving long-term reliability and miniaturization of the LN modulator chip. FOC has succeeded in stabilizing the bias voltage DC drift, which has been a challenge for thin-film LN modulators, by using basic LN modulator technology that FOC has been cultivating over many years. FOC is continuing this technology innovation to contribute to society’s needs for higher bandwidth capacity.
Development Background and Challenges
Internet data, video and other communications are growing exponentially due to the popularity, speed and efficiency of 5G mobile, cloud business and online services. Along with these inflating traffic demands, there is a need to further increase the density and capacity of communications devices used in optical networks, spurring on the need for miniaturization and higher integration of optical components.
The OIF (The Optical Internetworking Forum) standardization of high-bandwidth coherent driver modulator (HB-CDM) (Fig.1), which integrates an optical modulator and a driver IC in a small package supporting up to 128 Gbaud, is now being further advanced with the inclusion of compact thin-film LN modulators.
 (Figure 1) Compact thin-film LN driver integrated coherent Modulator (Package length 30 mm) |
Research on thin-film LN modulators (Fig.2) has attracted much attention over the years as a technology that can achieve both miniaturization and high capacity, which are difficult to achieve with conventional bulk LN modulators. There have been many research results reported on their performance potential. However, DC drift, which is an important characteristic of bias control essential for practical use, had not yet reached the level of practical application.
FOC Technology development
FOC has been the world leader in the market for coherent communications components, producing cutting-edge optical transmitters and receivers for the coherent communications market. In 2021, cumulative sales at FOC exceeded more than 1 million coherent LN modulators, maintaining the world's top share (*2). With FOC’s knowledge of bulk LN modulators accumulated over many years and by using a technology to optimize the structural and process parameters of thin-film LN modulators, DC drift has now been stabilized at a practical level and with a long-term reliability of 20 years established (Fig.3), a world’s first!
 (Figure 2) Thin-Film LN Modulator (sectional view) |
 (Figure 3) DC drift characteristic |
Key Features of thin-film LN
・Substantial miniaturization has been achieved using thin-film LN technology with 60% reduction in product packaging compared to bulk LN modulators
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・Achieved DP-IQ MZ (Mach-Zehnder type) modulator chip that can be mounted on OIF-based HB-CDM (* 3)
・HB-CDM devices using thin-film LN are pin compatible and have the same package size as those using compound semiconductor modulators, such as InP
・Excellent optical performance can be achieved with low wavelength dependence. With the recent increase in transmission bit rates and desire to achieve wavelength efficiency in DWDM systems, there is a growing need for wavelength expansion from the conventional C-band to the Super C-band (C++ band) and L-band. LN modulators are superior to InP modulators in terms of wavelength dependency, enabling seamless expansion of the wavelength range to the C/L band. Our thin-film LN modulators can enable this expansion of optical fiber transmission capacity.
・Excellent higher linearity can be achieved compared to compound semiconductor modulators, such as InP, and do not require temperature control by TEC (Thermo Electric Cooler), resulting in excellent controllability and power saving.
Future Developments
In April 2022, FOC plans to begin offering samples of the 128 Gbaud HB-CDM which is equipped with this thin-film LN modulator. In addition, by using our excellent process technology and design optimization of our ultra-wideband performance, we will continue to advance our technology innovation towards practical 200 GBaud applications.
Fujitsu Optical Components is going to exhibit at the 21 Optical Fiber Communications Technology Fair (FOE 2021) at Makuhari Messe in Chiba Prefecture from October 27, 2021 to 29th. Please visit the Fujitsu booth when you come to the event.(*4)
The Sustainable Development Goals (SDGs) adopted by the United Nations in 2015 represent a set of common goals to be achieved worldwide by 2030. Fujitsu’s purpose — “to make the world more sustainable by building trust in society through innovation”—is a promise to contribute to the vision of a better future empowered by the SDGs.
Notes
(*1) *About LN Modulator
LN modulators are discrete devices that convert an electrical data signal into an optical data stream via the electro-optic effect of a LiNbO3 crystal. Intensity modulators convert input electrical signals to optical intensity signals, while phase modulators convert them to optical phase signals. One of the LN modulator's features is modulation with minimal wavelength chirping. This is a desirable characteristic for ultra high-speed, long haul, and DWDM (Dense Wavelength Division Multiplexing) transmission.
(*2)https://www.fujitsu.com/jp/group/foc/subsidiary-gig5-sample/about/resources/news/press-releases/downloads/20210331.html
(*3)OIF Implementation Agreement OIF-HB-CDM-02.0
(*4)Visitor Ticket Request (FREE):https://www.foe.jp/ja-jp/visit/visiting.html
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Contacts
Fujitsu Optical Components Limited.
E-mail： foc-contact-pr@dl.jp.fujitsu.com