What is the expected collection timeline for shipments made in the second half of the quarter in Greater Asia
f of the year.
And we have some other iron in the fire, so to speak. So I think to distinguish indium phosphide, let's say, back in 2014 and '15, we have very nice growth, but that was the main growth engine was PON's business. And then we have the silicon photonics coming on strong. But now we're seeing multi-prong multi-point of growth.
They are not necessarily related with each other, but they also are connected to the benefit of using indium phosphide either for the wavelengths they produce, which can transfer data very quickly within a fiber optic transmission line, or their specific wavelengths can monitor health parameters in a specific application. So I think those are very exciting fields. I think we should see continued growth for many years to come.
Gary Fischer -- Chief Financial Officer
Yes. Let me just link that to one of the comments I made in my prepared comments, that we didn't have any 10% customers for the second quarter in a row. So that's another way to illustrate the diversity of the applications for indium phosphide. It's kind of a renaissance for indium phosphide, just lots of interesting things happening.
And one of the benefits, the things that we like about the business model is once you get into an application, it can have a long trajectory in terms of the useful life. It can last a long time.
Richard Shannon -- Craig-Hallum Capital Group -- Analyst
Great. I appreciate that.
Gary Fischer -- Chief Financial Officer
Thank you.
Richard Shannon -- Craig-Hallum Capital Group -- Analyst
Thank you guys.
Operator
[Operator instructions] And your next question comes from the line of Hamed Khorsand from BWS Financial. Please go ahead.
Hamed Khorsand -- BWS Financial -- Analyst
Hi Gary, could you just talk about the inventory going up so much and your accounts receivable going up so much the last quarter? Is there something you're planning from your customers that your inventory has soared so much versus revenue? And the same thing with receivables, I guess, are you providing extending out credit terms? Or is revenue just coming in toward the very end of the quarter?
Gary Fischer -- Chief Financial Officer
Yes. Well, let's stick on AR for a second. The AR it expanded for two reasons. One is increased revenue, that's fine, of course.
But the second is that the day sales outstanding shifted in the wrong direction. So for the previous quarters, from the last previous four quarters, if you average the DSOs by quarter, it comes to 81.75 days, which it's not a great DSO. It's never been a strength for us. Part of that is because we have so many sales in Greater Asia.
And just frankly, in case people don't know, but there's a lot longer time to pay in China, Korea, Japan. So the DSO went up by eight days to 90 days, which would be worth about $3 million into the accounts receivable. So if we had stayed with the previous four-quarter average, the AR would would not have gone up as much. It would have still gone up because of sales, but it would have been $3 million less.
As regards so there's no extended terms. There's no special deals. We're not aware of anyone that is going to become bad debt. We don't have any of those kind of problems, generally.
It's stretched. And it's probably also, and I didn't have time to do the analysis. But if we ship in the second half of the quarter, then we're not going to collect in the same quarter. So in the case of Greater Asia, if we ship any time after the first 20 days, we probably won't collect it in the same quarter.
So as for inventory, there's a couple of things going on there. Number one is we're growing and our production and management people and schedulers tend to stock up when they see growth on the horizon, which they are. We have a weekly production control meeting, which Morris attends. And so everyone's tied into what's happening in the company and the opportunities and the things that we're addressing.
The second thing that's happening is we did buy ahead on raw materials because we have visibility about raw material. That's one of the benefits of owning all t
f of the year.
And we have some other iron in the fire, so to speak. So I think to distinguish indium phosphide, let's say, back in 2014 and '15, we have very nice growth, but that was the main growth engine was PON's business. And then we have the silicon photonics coming on strong. But now we're seeing multi-prong multi-point of growth.
They are not necessarily related with each other, but they also are connected to the benefit of using indium phosphide either for the wavelengths they produce, which can transfer data very quickly within a fiber optic transmission line, or their specific wavelengths can monitor health parameters in a specific application. So I think those are very exciting fields. I think we should see continued growth for many years to come.
Gary Fischer -- Chief Financial Officer
Yes. Let me just link that to one of the comments I made in my prepared comments, that we didn't have any 10% customers for the second quarter in a row. So that's another way to illustrate the diversity of the applications for indium phosphide. It's kind of a renaissance for indium phosphide, just lots of interesting things happening.
And one of the benefits, the things that we like about the business model is once you get into an application, it can have a long trajectory in terms of the useful life. It can last a long time.
Richard Shannon -- Craig-Hallum Capital Group -- Analyst
Great. I appreciate that.
Gary Fischer -- Chief Financial Officer
Thank you.
Richard Shannon -- Craig-Hallum Capital Group -- Analyst
Thank you guys.
Operator
[Operator instructions] And your next question comes from the line of Hamed Khorsand from BWS Financial. Please go ahead.
Hamed Khorsand -- BWS Financial -- Analyst
Hi Gary, could you just talk about the inventory going up so much and your accounts receivable going up so much the last quarter? Is there something you're planning from your customers that your inventory has soared so much versus revenue? And the same thing with receivables, I guess, are you providing extending out credit terms? Or is revenue just coming in toward the very end of the quarter?
Gary Fischer -- Chief Financial Officer
Yes. Well, let's stick on AR for a second. The AR it expanded for two reasons. One is increased revenue, that's fine, of course.
 But the second is that the day sales outstanding shifted in the wrong direction. So for the previous quarters, from the last previous four quarters, if you average the DSOs by quarter, it comes to 81.75 days, which it's not a great DSO. It's never been a strength for us. Part of that is because we have so many sales in Greater Asia.
And just frankly, in case people don't know, but there's a lot longer time to pay in China, Korea, Japan. So the DSO went up by eight days to 90 days, which would be worth about $3 million into the accounts receivable. So if we had stayed with the previous four-quarter average, the AR would would not have gone up as much. It would have still gone up because of sales, but it would have been $3 million less.
As regards so there's no extended terms. There's no special deals. We're not aware of anyone that is going to become bad debt. We don't have any of those kind of problems, generally.
It's stretched. And it's probably also, and I didn't have time to do the analysis. But if we ship in the second half of the quarter, then we're not going to collect in the same quarter. So in the case of Greater Asia, if we ship any time after the first 20 days, we probably won't collect it in the same quarter.
So as for inventory, there's a couple of things going on there. Number one is we're growing and our production and management people and schedulers tend to stock up when they see growth on the horizon, which they are. We have a weekly production control meeting, which Morris attends. And so everyone's tied into what's happening in the company and the opportunities and the things that we're addressing.
The second thing that's happening is we did buy ahead on raw materials because we have visibility about raw material. That's one of the benefits of owning all t