Demand trends remain robust across our business, which contributed to revenue reaching $543.3 million, more than $13 million above the high end of our guidance.
We continue to execute very effectively with revenue upside falling to the bottom line as reflected in our non-GAAP net income of $1.45 per share, which was also above our guidance range.
From a revenue perspective, we had a particularly strong quarter for optical communications, which grew 10% from the fourth quarter and 24% from a year ago.
During our last call, we estimated that we would see a $25 million to $30 million revenue headwind in the first quarter from these constraints.
Operationally, I'm very happy to announce that our COVID-19 vaccination program for employees in Thailand has been a great success and that, at this point, 99% or virtually all of our employees in Thailand are now fully vaccinated.
This building will add approximately 1 million square feet or 50% to our global footprint, substantially increasing our manufacturing capacity.
Revenue of $543.3 million was well above our guidance and represented an increase of 7% from the fourth quarter and 24% from a year ago.
As we continue to execute very efficiently, our top line outperformance fell to the bottom line, with non-GAAP earnings of $1.45 per diluted share, which also exceeded our guidance.
This result includes approximately $0.05 per share in foreign exchange gains, offsetting the expenses related to our vaccination program that we incurred in Q1.
Optical communications revenue was $427.3 million, up 10% from the fourth quarter and made up 79% of total revenue.
Within optical communications, telecom revenue increased 9% from the last quarter to $338.6 million, a new record, and datacom revenue of $88.7 million increased 15% from Q4.
By technology, silicon photonics products reached a record $135.1 million or 25% of total revenue and was up 23% from the fourth quarter.
Revenue from products rated at speed of 400 gig or higher was $173.3 million, up 30% from the fourth quarter and 149% from a year ago.
Revenue from 100 gig product increased modestly from Q4 to $135.6 million.
Nonoptical communications revenue was $116 million or 21% of total revenue, representing a 25% increase from a year ago, but a decrease of 5% from the fourth quarter.
With the majority of our sensor revenues serving automotive applications, we are now reclassifying automotive revenue and other nonoptical communications revenue to include historical sensor revenue, which has represented less than 1% of quarterly revenue for the past two years.
On this combined basis, automotive revenue was $48.2 million, a decrease of 8% from last quarter.
While we don't intend to break this out in the future, for a more direct comparison purposes, automotive revenue, excluding sensors, declined 8% sequentially.
Industrial laser revenue was $37.5 million, a decline of 9% from Q4, but stable when viewed on a trailing 12-month basis.
Other nonoptical communications revenue was $30.3 million, up 7% from the fourth quarter.
Gross margin was 12.1%, down 20 basis points from Q4, consistent with our expectation, considering the expenses related to our vaccination program annual merit increases.
Operating expenses in the quarter were $13.2 million or 2.4% of revenue, resulting in operating income of $52.5 million or 9.7% of revenue.
Effective tax rate was 1.2% in the first quarter, and we continue to anticipate that our tax rate in the fiscal year 2022 will be approximately 3%.
Non-GAAP net income was a record at $54.2 million or $1.45 per diluted share.
On a GAAP basis, net income was $1.20 per diluted share.
At the end of the first quarter, cash, restricted cash and investments were $528.6 million, compared to $548.1 million at the end of the fourth quarter.
Operating cash flow was $39 million.
With capex of $34.6 million, free cash flow was $4.4 million in the quarter.
We remain committed to return surplus cash to shareholders through a 10b5-1 share repurchase plan, combined with opportunistic open market share buybacks.
Currently, we have $81.2 million in our share repurchase authorization.
We estimate that the ongoing supply cost change will again impact our second quarter revenue by approximately $25 million to $30 million.
With that backdrop, for the second quarter, we anticipate revenue in the range of $540 million to $560 million.
From a profitability perspective, we anticipate non-GAAP net income to be in the range of $1.42 to $1.49 per diluted share.

Summary:
We continue to execute very effectively with revenue upside falling to the bottom line as reflected in our non-GAAP net income of $1.45 per share, which was also above our guidance range.
Revenue of $543.3 million was well above our guidance and represented an increase of 7% from the fourth quarter and 24% from a year ago.
As we continue to execute very efficiently, our top line outperformance fell to the bottom line, with non-GAAP earnings of $1.45 per diluted share, which also exceeded our guidance.
Non-GAAP net income was a record at $54.2 million or $1.45 per diluted share.
On a GAAP basis, net income was $1.20 per diluted share.
With that backdrop, for the second quarter, we anticipate revenue in the range of $540 million to $560 million.
From a profitability perspective, we anticipate non-GAAP net income to be in the range of $1.42 to $1.49 per diluted share.