Development of New Pump Source FRSi4XX Series for Forward Raman Amplifiers
- Achieves Higher Speeds and Long-Distance Transmission -

March 10, 2020

  • The rapid increase in communications traffic in recent years is demanding technological innovation in ultrahigh-speed optical fiber communications.
  • We have developed new pump sources for forward Raman amplifiers capable of extending transmission distance.
  • Our company will continue to develop technologies that support high-speed, high-capacity, and long-distance optical communications so that we can make significant contributions to advance convenient lifestyles through 5G and other technologies.

Furukawa Electric Co., Ltd. (Head Office: 2-2-3, Marunouchi, Chiyoda-ku, Tokyo; President and CEO: Keiichi Kobayashi) has developed FRSi4XX Series pump sources for forward Raman amplifiers that extend transmission distances in ultrahigh-speed optical fiber communication more than conventional systems.


Proliferation of smartphones has led to a dramatic increase in communication traffic, including the expansion of wireless backbones, cloud computing, video streaming, and the penetration of social networks. To deal with this traffic explosion, improvement in optical signal-to-noise ratio (OSNR;(note 1)) is becoming an important factor in soon-to-be-deployed ultrahigh-speed optical fiber communications such as 400 Gbps and beyond. Existing erbium-doped fiber amplifiers (EDFA;(note 2)), which are widely used in current systems, do not have sufficient OSNR performance. Demand is increasing for Raman amplifiers(note 3) due to their excellent noise characteristics. Forward Raman amplifiers, which make the most of the advantages of Raman amplification, are expected to be a technology necessary for increasing transmission distances(note 4).

In the past, only the backward Raman amplifiers was used due to limitations of the noise characteristics of the pump source. Furukawa Electric’s FRSi4XX Series novel pump sources make it possible to realize forward Raman amplifiers and featuring high output as well as excellent low-noise characteristics.


The features and development points of the FRSi4XX Series are as follows:

High power output

Furukawa Electric achieved a high-output chip structure and high-efficiency coupling technology by leveraging the design, manufacturing technology and high-precision packaging technology of the InP (Indium Phosphide) optical semiconductor chips. The optical output of 100 mW or more was achieved through an optimized heat dissipation design.

Low noise

The FRSi4XX pump series reduces noise by about 20 dB/Hz compared with conventional pump sources for Raman amplifiers.

Combining the FRSi4XX Series with existing FOL1439 Series, yield pump sources especially well-suited to forward pumping Raman amplifiers.
As demand for ultrahigh-speed optical fiber communications continues to grow, we will further enhance the technology of this series and contribute to the construction of information and communications infrastructure in anticipation of the advancement of 5G. Sample shipments of the FRSi4XX Series are scheduled to begin in the second half of FY2020.

Type name FRSi4XX Series
Optical output (mW) >100
Noise characteristic RIN (dB/Hz) <-130(~3GHz)
Operating condition EOL(note 5), Ts=25℃、Tc=70℃
Wavelength (nm) 1420 to 1500
Wavelength spectrum width (nm) >25


(note 1)OSNR stands for Optical Signal to Noise Ratio. It is defined as the ratio of optical signal power to optical noise power. Improvements in OSNR contribute to the extension of transmission distances.

(note 2)EDFA stands for Erbium Doped Fiber Amplifier. An EDFA is an optical fiber amplifier in which erbium is added to the core of the optical fiber. It is currently widely used in wavelength division multiplex (WDM) systems. Wavelengths around 1550 nm can be amplified with excitation light of 980 nm or 1480 nm.

(note 3)Raman scattering occurs in a wavelength region that is about 100 nm longer than the excitation light wavelength. When an optical signal exists in this scattered light region, it is amplified by stimulated Raman scattering and can be used as an amplifier. Although its excitation efficiency is lower than that of an EDFA, it is widely used because it has excellent features such as a wide amplification band, the ability to amplify an arbitrary wavelength range and low noise interference through the use of optical fiber as an amplification medium. Transmission of excitation light in the same direction as the optical signal is called forward pumping, whereas transmission in the opposite direction as the optical signal is called backward pumping.

(note 4)Refer to the news release, “Development of New Pump Source Technology for Raman Amplification” published by Furukawa Electric on March 6, 2019.

(note 5)EOL stands for End of Life.

Furukawa Electric Group’s efforts towards the SDGs

Based on the corporate philosophy of “Drawing on more than a century of expertise in the development and fabrication of advanced materials to contribute to the realization of a sustainable society through continuous technological innovation,” the Furukawa Electric Group is conducting business activities centered on four core technological capabilities (metals, polymers, photonics and high frequency). Moreover, keeping in mind the “Sustainable Development Goals (SDGs)” adopted by the UN, we formulated the “Furukawa Electric Group Vision 2030,” which clarified the business areas of the Furukawa Electric Group, and are advancing efforts aimed at “creating solutions for the new generation of global infrastructure combining information, energy, and mobility to build a sustainable world and make people’s life safe, peaceful, and rewarding.