The optical transport equipment market in June reached its highest quarterly revenue level in more than five years, according to Dell’Oro Group.

Combined worldwide revenue for wavelength-division multiplexers (WDM) and Sonet and optical switches grew 8% sequentially to about $2.7 billion in the second quarter, Dell’Oro said. That represents growth in the mid to low single digits from a year earlier. It’s also the highest quarterly revenue the sector has achieved since early 2002.

Metro WDM gear in particular is driving much of the sector’s growth, Dell’Oro analyst Jason Suey said. But sales of legacy Sonet gear are surpassing expectations as well. More than half of the total optical revenue in the quarter came from Sonet gear. Sonet revenue has generally flattened out as carriers look to next-generation technologies, but it grew in the mid to high single digits sequentially in the second quarter.

Geographically, the growth seen in the optical sector came from all major regions of the globe, Dell’Oro said.