By Bengt O. Hallberg

In 1981, I found myself facing a dilemma. After spending a year working on my Master of Science in Engineering Physics thesis and another year working as a scientist at IOF/KTH, I completed a project on the fundamental theory of photon propagation in optical fibers and measurement technology. I then continued working as a scientist and pursuing my Ph.D. at the same time, doing pioneering research on WDM. Within three years, I had become a leading expert in the field. However, Ericsson, a stakeholder in the project and a Swedish telecommunications company, announced that it was no longer interested in the technology.

BOH Optical AB 1981-

I then decided to continue the project on my own. It began 1981 with an assignment in a different field of photonics. The task was to develop a measuring instrument for environmental research for the Stockholm University. The Board for Technical Development (STU) financed the project, they required me to start a company to run it. Thus began BOH Optical AB. Later, the university itself wanted to end the project, which was fine with me.

Thanks to the excellent cooperation with the case officer at STU Sven Ingmar Ragnarsson, who himself had been a scientist in photonics, I received support to develop a WDM system.

An external stakeholder was also needed. Since Ericsson was not interested, the Swedish PTT was the only option left. Point of contact was Olle Blomdin.

At that time, telecommunications markets around the world were closed off to competition, often operating as monopolies. The Swedish PTT was one such example. I later learned that their monopoly only extended to switchboards and not the rest of the network. However, in the public consciousness, they were perceived as having a monopoly on everything.

I initially ran the company's operations from my home, but I now needed a small industrial premises in which to build a laboratory. I found the perfect location at Gårdsvägen 2 in Solna, a town adjacent to Stockholm. That's where we developed and designed the first three-channel WDM system with me as self-starter and project manager.

The manufacturing of some subcomponents was outsourced to subcontractors. One such company was the high-tech NKT Electronics in Denmark able to manufacture digital electronics for a transmission speed of 140 Mbit/s, which was state of the art at the time. This technique was chosen to feed video and audio signals to BOH Optical AB's patented TX modules. The laser diode wavelengths were stabilized using a more advanced and unique method than the one I had worked on at IOF.

TX modules convert electronic digital signals into optical signals for WDM transmission. They generate photon pulses of different wavelengths, which are then combined in an MUX module. The company developed its own version of it. The MUX was connected to a fiber optic cable, which in turn was connected at the other end to a DMUX that the company also had developed. In those the optical wavelengths are divided and distributed to the RX modules. They then convert the optical digital signals back to the original electronic ones. During this early stage of development, cables with multimode gradient index fibers were used.

I had been in contact with Professor Palle Jeppesen at the Technical University of Denmark (DTU) in Lyngby, just outside Copenhagen, since the 1970s. It was through him that I learned about NKT.

Swedish Radio's Science desk broadcast October 3, 1979

On October 3, 1979, forty-seven years ago, the Swedish Radio's Science desk broadcast the state of the art in optical fiber technology for photon transmission in a telecom context at that time. Few people knew that this was even going on. Perhaps this was the first comprehensive, serious feature on the subject in Sweden. I was interviewed about the scientific part of it.

Katarina Ahnlund, the journalist who interviewed me, was the first woman in Sweden to earn a M.Sc. in Engineering Physics. She earned it at KTH in Stockholm. She was also the first woman to earn a doctorate in technology. Ahnlund specialized in nuclear physics. She worked in Sweden and the U.S. with Nobel Prize winners, one of whom was her mentor. In 1969, she was hired to establish Swedish Radio's science desk. Ahnlund worked there until she passed away.

Open house event May 17, 1983

The laboratory and office on Gårdsvägen were completed in 1983. On May 17 of that year, the company held an open house. It was a success! Twenty-four people attended that day, and another fifty or so visited later that year. Virtually everyone of significance in Swedish photonics academia and industry visited.

Much of the ongoing WDM project was conducted in secrecy and was therefore not shown. However, the photonics and the company's expertise were open to anyone who was interested.

I was particularly pleased that Professor Emeritus Erik Ingelstam attended the event. He was a former professor of optics (Physics II) at KTH and founded IOF in 1955. Professor Klaus Biedermann took over his roles. In 1978, he was appointed professor and the following year, in 1979, he became Director of the IOF until the institute merged with AB Acreo.

On May 27, a special event was held for the IOF scientists led by Biedermann. I was delighted to meet my former colleagues again. Stefan Johansson, principal investigator of the classical optics group, and Leif Stensland my former supervisor, had participated on May 17.

Dr Michael Salour

At that time, a young man was working on his thesis for a Master’s of Science degree at my company in Solna and in another company in the US. His name is Martin Kull. I arranged a position for him with a colleague of mine, the late Dr. Michael Salour, who owned Tacan Corp. in Carlsbad, California. His company was contemporary with mine. Martin later earned a Ph.D.

Ragnarsson established contact between us when Salour was still a professor at MIT in the US. We got to know each other when I visited there. In turn, he made his first visit to my company on June 20, 1983. We kept in touch over the years. Our last contact was on the phone on November 1, 2023, when he called me.

Tragically, he passed away fourteen days later, on November 15, in a plane crash. Among other things, we had talked about this year's Nobel Prize in Physics, which was about attosecond pulses. He knew that I used to attend the Nobel laureates lectures at Stockholm University before the award ceremony on December 10. The idea was that I would tell him about it before Christmas, when we used to be in touch.

Next blog

I finish with that sad story. The website will be updated with the 1979 interview I mentioned in the text. It will be published at the same time as my third blog post about the development of the uniqe transmitter to the world's first WDM system on Tuesday March 3, 2026.

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