Moore’s law reflects how the number of transistors on a Silicon integrated chip grows over time, as the technology to miniaturise transistors improves. Since the 1970s the number of transistors on a Silicon integrated circuit has roughly doubled every two years. What started as an observation of historic evidence and a projection seems to have become an ongoing reality driven by industry expectations.
Optical fibre was introduced into networks in the late 1970s when the attenuation per km fell below 4dB. In the 1980s singlemode optical fibre started to be deployed in volume in core networks. My optical transmission experience started in the UK where initial commercial speeds of 140Mbit/s soon became 565Mbit/s (see graph). SDH arrived in the 1990s and speeds climbed to 2.5Gbit/s. The invention of the Erbium doped fibre amplifier, and its use in optical systems, made wavelength division multiplexing (WDM) viable in the 1990s. Initially offering multiple 2.5Gbit/s per wavelength, then soon moving to more wavelengths and 10Gbit/s by the end of the century. Higher speeds per wavelength depend on coherent detection with 100Gb/s common, 200Gbit/s arriving and 600Gbit/s now available.
Plotting the commercial capacity of optical fibre on a logarithmic scale shows its growth is very similar to that of transistor count, doubling roughly every two years. I am sure the relationship is not accidental, computers without connectivity are useful, but connected computers drive the ICT revolution we are living through. Doubling of data generation and processing every two years drives doubling of data transmission. I strongly suspect the doubling of transistors on an integrated circuit and the doubling of commercial optical fibre capacity hides the much greater increase in deployed computers and deployed optical fibre.
However, there are big differences between investment in integrated circuits and optical fibre. For example, to take advantage of the increased capability of integrated circuits requires a new computer. To take advantage of increasing optical fibre capacity does not require new fibre.
Interestingly, optical fibre deployment almost always costs a lot more than the optical fibre (even when cabled). Once installed optical fibre capacity can be boosted through the use of new transmission equipment. Even the single mode optical fibre deployed in the 1980s has the capability to carry the latest transmission formats. Once installed this does not need replacing.
Evidence from deployed fibre shows in-service life over 30 years with no degradation and there is no industry accepted “wear-out” mechanism. Yes, it can fail and its natural enemy, the JCB, can damage it. I believe optical fibre, deployed in modern plastic ducts, should have a service life in excess of 50 years, with 100 years not being unreasonable.
So once optical fibre is deployed, the user can benefit from improvements in optical equipment without replacement. Using ECI as an example, we can see, not only does the capacity per wavelength increase, but the space required to host the capacity remains constant. For the last seven years a 30 times increase in transmitted capacity results in no increase in equipment size. See the chart below:
In case I have not driven my point home, I applaud the revolution in electronics, but feel the glory of our connected world needs to be shared between Silicon (chipsets) and Silicon Dioxide (fibre), along with the associated opto-electronic components which continue to deliver exponential transmission capacity growth.
Dr. Antony Thorley C.Eng., FIET has over 35 years of telecommunications experience with vendors, operators and regulators, working on reviews of the business connectivity market. Currently Tony supports pre-sales technical work supporting the UK sales team and the UK market for ECI on DWDM, OTN, packet and network management for customers in the service provider, utility and data centre markets. He started his career with optical component specification and evaluation including early work on coherent transmission and optical amplifiers. Then moved to circuit design, sub-system design, system design and analogue ASIC development. His career has included over time: marketing, customer engineering, network strategy and regulation.