You are given a text that consists of multiple sentences. Your task is to perform abstractive summarization on this text. Use your understanding of the content to express the main ideas and crucial details in a shorter, coherent, and natural sounding text. 
Text: With me on the call today are Seamus Grady, Chief Executive Officer; and Csaba Sverha, Chief Financial Officer.
We had an excellent fourth quarter to finish a strong fiscal year with robust demand trends continuing across our business combined with excellent execution by our team, we delivered a number of records in the quarter.
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.
Looking at some of the highlights of the fourth quarter.
Optical communications revenue reached another new record, driven by strong telecom demand.
Non-optical communications revenue also reached another record in Q4.
Looking ahead, we remain encouraged by healthy demand trends across all lines of business as we continue to successfully navigate and manage component supplies.
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.
Despite this headwind, we anticipate that revenue will continue to grow sequentially to a new record in Q1 as Csaba will outline in a moment.
We are also optimistic from a profitability standpoint.
That said, in Q1, we anticipate a small non-recurring headwinds to net income.
As you may have heard, Thailand, along with other countries in Southeast Asia has recently seen a rapidly growing number of COVID-19 cases.
In response, lockdowns and other measures have been imposed, which primarily impact social gatherings.
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.
This includes increased testing and sending people home with pay, if they test positive for COVID-19.
In addition, we have been granted permission by the Thai government to vaccinate our employees and have been carrying out this initiative for the past several weeks at our expense.
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.
We are proud to be able to carry out this effort that has both a very positive social impact, while also being good for our business, and we believe it will further enhance our very favorable reputation as an excellent employer in Thailand.
As we communicated earlier this year, we have broken ground on a new 1 million square foot building at our Chonburi campus.
Construction is progressing and we expect the building to be complete in about one year.
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.
This size will enable us to relocate some non-manufacturing activities from the current campus, which will allow us to increase our manufacturing footprint within our existing buildings.
As a result, we are confident that we will continue to have ample capacity to satisfy the growing customer demand we are experiencing.
In summary, we had a very strong finish to a record year.
We are optimistic about demand trends from all the markets we serve and we are well positioned to continue to deliver excellent results over the longer term.
We had a strong finish to a record year with record revenue and non-GAAP earnings.
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.
Looking at revenue in more detail.
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.
In Q1, we expect the optical communications growth trend to continue.
Looking at our non-optical communications business.
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].
Now turning to the details of our P&L.
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.
This is primarily due to the reversal of evaluation allowance related to certain subsidiaries as a result of better operating performance and effective control of operating expenses.
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.
Note that the Cisco revenue contribution includes a partial year impact from Cisco's acquisition of Acacia.
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.
Turning to the balance sheet and cash flow statement.
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.
Now, I would like to turn to our guidance for the first quarter of fiscal year 2022.
We are entering the year from a position of strength and remain optimistic about the markets we serve, and our ability to execute.
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.
We believe this employee safety costs are non-reoccurring, and that this program benefits our employees and their families, as well as the continued operational success of our business.
If not for these non-recurring costs, our non-GAAP net income guidance for Q1 would have represented another quarterly record for the Company.
In summary, we are proud of our record fourth quarter and fiscal 2021 performances.
We are excited about the prospects ahead and look forward to continued success for all our stakeholders.

user
sees q1 revenue $510 million to $530 million.
q4 revenue $509.6 million versus refinitiv ibes estimate of $487.5 million.
q4 non-gaap earnings per share $1.31.
q4 gaap earnings per share $1.13.
sees q1 non-gaap net income per diluted share to be in range of $1.29 to $1.36.

assistant