Setback for IPG in fiber laser court battle

30 Dec 2010

Judge decides to adopt IMRA's "mode converter" definition, after IPG sought to re-define some key terms in the pair's litigation fight.

After almost four months of silence, the ongoing court battle between fiber laser specialists IPG Photonics and IMRA America has sparked back into life, following a technical order in favor of IMRA.

On December 27, Senior US District Judge Arthur Tarnow ordered that IMRA’s “mode converter” definition would be adopted for the purposes of instructing the jury, and declined IPG’s request for an alternative description.

“Specifically, in the context of this litigation and for purposes of jury instruction, a ‘mode converter’ shall be defined as ‘an element capable of matching the mode of a multi-mode amplifier fiber’,” he concluded.

The case revolves around the claims contained within US patent 5,818,630 – filed by IMRA in June 1997 – and whether or not IPG’s fiber laser products infringe it. Since IPG dominates the fiber laser sector with a market share in excess of 60%, and IMRA has already agreed licensing deals with many other fiber laser makers, the court case is likely have a key bearing on the future of the sector.

Heart of the matter
And at the heart of the so-called ‘630 patent claims is a key component, which IMRA had labeled a “mode converter”. This is the component that launches a beam of light into the input end of a multi-mode fiber, in such a way that the beam is preserved in its fundamental mode and generates a high-energy output.

Following IMRA’s initial complaint in 2006, IPG requested a re-examination of the ‘630 patent. In mid-2009, the US Patent Office confirmed the validity of the claims within the patent and IPG’s request for a second examination was rejected by the court. IPG then asked for that rejection to be reconsidered – about which a decision is still awaited.

Meanwhile, IPG had sought to re-define exactly what was meant by the phrase “mode converter”. IMRA’s preferred construction, for subsequent use in explaining the case to a jury, was as follows:

An element capable of matching the mode of a multi-mode amplifier fiber

IPG sought to have that construction re-defined as:

An optical imaging system, such as a lens system, a section of tapered fiber, or a combination thereof, capable of matching the mode of the multi-mode fiber amplifier.

Judge Tarnow gave lengthy consideration to both IPG’s claims that the IMRA term “element” could encompass any manner of structure, and those of IMRA - that IPG’s suggestions were too limited in scope, and that a tapered single-mode fiber was not an example of an optical imaging system.

IPG also sought to re-define three other terms contained within the claims of the ‘630 patent, arguing that:

“converting the mode of the input beam to match a fundamental mode of the multi-mode fiber amplifier” ought to be changed to read: “converting the mode of the input beam to cause it to match a fundamental mode of the multi-mode fiber amplifier”;

“mode-converted input beam” to: “an input beam whose mode has been converted to match a fundamental mode of the multi-mode fiber amplifier”; and

“an amplified beam substantially in the fundamental mode” to: “an amplified beam having substantially all of its energy content in the fundamental mode”

Exercise in redundancy
In his discussion of those requests, Judge Tarnow said that the three terms did not require any further clarification by the court, and that doing so would “verge on constituting an exercise in redundancy”. Tarnow decided only to construe the key phrase “mode converter”, which lies at the heart of the dispute and appears on a number of occasions in the ‘630 patent.

Ultimately, he rejected the IPG version, on the basis that the mode converter is not necessarily an optical imaging system, as implied by the company’s preferred description. “To do so would impermissibly narrow the scope of the claim,” wrote Tarnow in his discussion.

He also rejected IPG’s objection to the phrase “element”, arguing that it would be hard to find a more neutral term to use, saying: “It is clear that the mode converter is conceived as a discrete component in the ‘optical amplification system’ described.”

IPG also asked for the wording within another IMRA patent, this time 7,190,511, which was filed about a year after the '630 patent, to be considered, saying that IMRA's own inventors had generally understood the term “mode converter” to mean “an optical imaging system”.

But, as Tarnow noted, the ‘511 patent contains neither of those phrases, and provided an insufficient basis upon which to adopt IPG’s preferred definition.

Having originally been due to commence on August 24, a new start date for the case is still awaited.