Revenue was well above our guidance range and for the first time exceeded $0.5 billion at $509.6 million.
In addition to record revenue, we also delivered record non-GAAP operating margins of 9.9%, resulting in an all-time high non-GAAP earnings per share of $1.31 in the fourth quarter.
For the full fiscal year, we produced record revenue of $1.88 billion, representing industry-leading growth of 14% from the prior year.
Non-GAAP net income was $4.67 per share.
Total operating cash flow for the year was $118.7 million and free cash flow was $76.1 million.
We estimate that the supply constraints we are experiencing impacted our fourth quarter revenue by approximately $25 million to $30 million, and we expect to see a similar impact in Q1.
Our manufacturing facilities are fully operational, but we have implemented additional safeguards beyond what we have been doing for the past 1.5 years in order to protect our staff.
We are very pleased that at this time the vast majority of our employees have already received their second doses, such that by the end of this month, approximately 90% of our employees in Thailand will be considered fully vaccinated.
As we communicated earlier this year, we have broken ground on a new 1 million square foot building at our Chonburi campus.
We also previously discussed our intention to add approximately 100,000 square feet of manufacturing space at our Pinehurst campus.
Just after the end of the fourth quarter, we completed the acquisition of 15 acres of land that had become available adjacent to our Pinehurst facility.
Revenue of $509.6 million, up 6% from Q3 and 26% from a year ago, and was above our guidance range.
We also executed very well, hit our highest gross margin in four years, and record operating margins to produce non-GAAP earnings of $1.31 per share, which also exceeded our guidance.
Optical communications was $387.8 million or 76% of total revenue, up 7% from Q3.
Non-optical communications revenue was $121.7 million or 24% of total revenue, and increased 4% from Q3.
Within optical communications, telecom revenue was $310.7 million, up 10% from last quarter.
Datacom revenue was $77.1 million, down very modestly from Q3.
By technology, silicon photonics products made up 22% of total revenue or $110.2 million, up 5% from Q3.
Revenue from products rated at speeds of 400 gig or higher was $133.3 million, up 27% from the prior quarter.
This more than offset a 4% sequential decline of 100 gig products to $133.6 million in the fourth quarter.
Automotive revenue was $48.6 million, a slight decline from our record third quarter results.
Industrial laser revenue more than offset this at $41.1 million, up 14% from the third quarter.
Sensor revenue was $3.6 million and other non-optical communications revenue was up 14% to $28.2 million [Phonetic].
Gross margin of 12.3%, up 10 basis points from Q3 and was at the highest level in four years.
Operating expenses in the quarter were $12 million or 2.4% of revenue, reflecting our operating leverage, resulting in operating income of $50.5 million or 9.9% of revenue, a record for the Company.
During the fourth quarter, we have recorded a tax benefit of $2.1 million.
We anticipate that our effective tax rate in fiscal year 2022 will be approximately 4%.
Non-GAAP net income was a record at $49.4 million or $1.39 per diluted share.
On a GAAP basis, net income was also a record at $42.4 million or $1.13 per diluted share.
For the full year, revenue was $1.88 billion, an increase of 14% from the prior year.
Non-GAAP gross margin was 12.1% and operating margins were 9.5% of revenue.
Non-GAAP earnings per share for the year was $4.67, up a strong 25% from fiscal year 2020.
We report 10% customers annually and in fiscal year 2021, we had three 10% customers.
Cisco and Lumentum both represented 14% of revenue and the Infinera represented 12% of revenue for the year.
Excluding the impact of the acquisition, Acacia would also have been a 10% customer in fiscal year 2021.
Our Top 10 customers represented 78% of revenue, compared to 79% in fiscal year 2020.
At the end of the fourth quarter, cash, restricted cash and investments were $548.1 million, an increase of $39.2 million from the end of the third quarter.
Operating cash flow was $43.5 million with capex of $13.5 million; free cash flow was $30 million in the quarter.
In addition to expenses related to construction at our Chonburi campus, the recently purchased 15 acres of land, adjacent to our Pinehurst campus that will facilitate the manufacturing expansion we have in progress at that campus.
Of the $13.2 million purchase price, 10% was paid during the fourth quarter and the remainder was paid in the first quarter of fiscal 2022.
We remain active in our share repurchase plan, and during the fourth quarter, we repurchased approximately 123,000 [Phonetic] shares at an average price of $85.88 for a total cash outlay of $10.5 million.
Approximately $81.2 million remains in our buyback authorization.
For the first quarter, we anticipate revenue in the range of $510-530 million, which will represent another record quarter for Fabrinet.
From a profitability perspective, we anticipate non-GAAP net income to be in the range of $1.29 to $1.36 per diluted share.
I'd like to point out that this guidance includes the impact of our customary annual merit increases as well as approximately a $0.04 to $0.05 impact from the cost we are incurring in order to safeguard our employees through the vaccination program that Seamus described.

Summary:
In addition to record revenue, we also delivered record non-GAAP operating margins of 9.9%, resulting in an all-time high non-GAAP earnings per share of $1.31 in the fourth quarter.
Revenue of $509.6 million, up 6% from Q3 and 26% from a year ago, and was above our guidance range.
We also executed very well, hit our highest gross margin in four years, and record operating margins to produce non-GAAP earnings of $1.31 per share, which also exceeded our guidance.
On a GAAP basis, net income was also a record at $42.4 million or $1.13 per diluted share.
For the first quarter, we anticipate revenue in the range of $510-530 million, which will represent another record quarter for Fabrinet.
From a profitability perspective, we anticipate non-GAAP net income to be in the range of $1.29 to $1.36 per diluted share.