The first quarter of 2021 was a generally positive one for the optical networking ecosystem punctuated by robust year-over-year revenue growth, according to a recent LightCounting report.

While the results were “mostly positive” for public cloud providers, communications service providers, and optical networking equipment and component vendors, the analysts warned of headwinds and uncertainty ahead.

”While the initial Q1 2021 results suggest a strong 2021 for the optical industry, we must remember there are larger forces at work and temper optimism with caution,” the analysts wrote

A global semiconductor shortage, the U.S. trade war with China, and delays to the Chinese 5G rollout were all cited as potential headwinds. Moreover, the analysts called out unforeseen impacts related to how quickly or robustly the U.S. economy recovers, the COVID-19 outbreak in India, and unrest in the Middle East.

Setting aside the unknown, vendors in the optical segment faired well during the first quarter of 2021, reporting revenues that were up an average of 40% from the year prior, according to LightCounting. Year-over-year revenue comparisons were artificially high, however, due to last year's onset of the COVID-19 pandemic and related sales deficits, the analysts explained.

Alibaba, Alphabet, Amazon, Facebook, and Microsoft — all major consumers of optical networking equipment — saw their revenues decline sequentially in Q1, but grow substantially from the same period in 2020. Alibaba and Facebook saw the strongest year-over-year rebound, up 77% and 48% respectively, followed closely by Amazon at 44%, Alphabet (Google) at 34%, and Microsoft at 19%.

Telecom equipment vendors reported collective year-over-year revenue growth of 10%, partially due to mandates from several European countries that are forcing operators to rip out and replace Huawei equipment.

Optical component vendors reported mixed results during the quarter. Eoptolink, which produces optical networking transceivers, saw record growth in Q1 with revenues of just over $100 million. However, companies like Lumentum, II-VI, Accelink, and Innolight, which produce components used in optical networking equipment, like transceivers, amplifiers, and laser pumps, saw steep quarter-over-quarter declines, according to LightCounting.

The analysts expect the optical transceiver market to stay above water in 2021, fueled by 100 Gb/s and 400 Gb/s Ethernet deployments by Chinese cloud companies and others, and growing demand for 400ZR pluggable coherent optics by hyperscalers.