Meeting optical communication demands with InGaAs photodiodes

This article originally appeared in the _May'24 magazine issue of Electronic Specifier Design – see ES's Magazine Archives for more featured publications.

Initially developed using Silicon, these photodiodes facilitated the detection of ultraviolet and visible light. Recent technological advancements have expanded their capabilities to include the detection of infrared light, utiliSing materials like Indium Gallium Arsenide for longer wavelengths. 

In the rapidly evolving field of telecommunications, the demand for high-data throughput has driven engineers to explore efficient emitters and detectors. This has led to the increased use of light in telecommunications – optical communication. The benefits include minimal interference, crucial in dense urban areas, and the ability to penetrate physical barriers. 

Moreover, light enables wireless data transmission over long distances, offering the potential to reduce infrastructure in remote areas. Near-infrared light, with its high frequency, allows faster data transmission and contributes to lower energy consumption in data centres. 

Indium Gallium Arsenide Photodiodes (InGaAs PD), play a vital role in advancing these technological frontiers. 

Benefits for optical communications

InGaAs (Indium Gallium Arsenide) PIN photodiodes offer several benefits for optical communication applications. 

Efficient signal conversion 

InGaAs PIN photodiodes exhibit high responsivity in the near-infrared range, typically between 1.7μm, short-wavelength enhanced types, and long-wavelength types having a cutoff wavelength extending to 1.9, 2.1 or up to 2.6μm. They are particularly well-suited for optical communication systems that operate in these wavelengths, such as fiber-optic communication systems. The high responsivity enables efficient conversion of optical signals into electrical signals, enhancing the detection sensitivity. 

High data rate transmission 

InGaAs PDs have a wide bandwidth response, allowing them to capture and detect optical signals with high data rates. They can handle high frequency modulated optical signals, making them suitable for high-speed optical communication systems. The wide bandwidth enables the detection of signals with high bandwidth capacity, facilitating high-data-rate transmission. 

Accurate and reliable detection 

Low dark current: dark current refers to the current generated by a photodiode in the absence of any incident light. InGaAs PIN photodiodes exhibit low dark current levels, which is essential for minimising noise and improving the signal-to-noise ratio (SNR) of the detected optical signals. Low dark current enables accurate and reliable detection of weak optical signals, enhancing the overall performance of optical communication systems. 

Long distance precision 

The InGaAs PD offers low noise characteristics, contributing to a high signal-to-noise ratio. The low noise performance allows for the detection of weak optical signals with high precision and accuracy. It is particularly important in long-distance optical communication systems where the received optical power may be relatively low. 

Reliable operation in demanding environments  

Exhibiting good temperature stability, InGaAs PDs maintain consistent performance over a wide temperature range. This stability is crucial in optical communication systems that operate in demanding environments where temperature variations are present. The temperature stability ensures reliable and consistent operation of the photodiodes, minimising the need for temperature compensation or additional measures to maintain performance. 

Integration with optical components 

InGaAs PIN photodiodes can be manufactured in compact sizes and package types, enabling integration into various optical communication devices and systems. Their small form factor makes them suitable for applications needing space-saving designs, such as optical transceivers and receivers. Integration with other optical components enhances the overall efficiency and performance of optical communication systems. 

These benefits make InGaAs PIN photodiodes well-suited for a wide range of optical communication applications, including long-haul fibre-optic communication, high-speed data transmission, and telecommunications networks where high-performance, low-noise detection is essential. 

Navigating optical advancements with new InGaAs PIN Photodiodes 

Hamamatsu Photonics has made speed its priority for the success of optical communication. This innovation complements its existing 25 and 50Gbps photodiodes. Leveraging optical design and manufacturing expertise, Hamamatsu has incorporated advanced techniques to maximise light guidance into a compact photosensitive area. This approach ensures an equivalent signal-to-noise ratio (S/N ratio) compared to standard products. 

The resulting InGaAs PIN photodiode operates effectively at low reverse voltage and demonstrates reliable performance in transmission bands up to 64Gbps at VR = 2V when paired with an optimised preamp. The culmination of its efforts is shown in its latest device, the G12183-210KA-03. Hamamatsu is actively working towards achieving even higher speeds in future sensor developments. 

In the realm of optical communication, harnessing the potential of near-infrared light stands out as a pivotal challenge in the coming years. Despite the manifold advantages presented by this light spectrum, it is not without its complexities. Concurrently, engineers worldwide are delving into the exploration of quantum communications, heralding a new era in secure and efficient data transfer. 

With a history in the design and production of optical components, Hamamatsu navigates the intricacies of advancing optical communication technologies. Hamamatsu consistently refines products to meet evolving optical communication challenges and is dedicated to supporting customer developments across a diverse array of applications.